Chapter 10 — Division of Polynomials
Class 8 (Maharashtra Board) — Important Q&A + Textbook Exercises
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- Polynomial: algebraic expression in one variable with whole-number exponents (e.g., \(x^2+2x+3\)).
- Degree: highest exponent (e.g., degree of \(3x^5+2x^2\) is \(5\)).
- Division by monomial: divide each term by monomial (e.g., \((6x^3+8x^2)\div 2x = 3x^2+4x\)).
- Division by binomial: use long division or synthetic (arrange descending powers and use 0 coefficients for missing terms).
Q1. What is the degree of \(7x^3+5x+2x^5+2x^2\)?
Ans: degree \(=5.\)
Q2. Is \(3x^{-1}+2\) a polynomial?
Ans: No — exponent \(-1\) is not a whole number.
Q3. Divide \(21m^2\) by \(7m\).
Ans: \(21m^2\div7m=3m.\)
Q4. Divide \(40a^3\) by \(-10a\).
Ans: \(40a^3\div(-10a)=-4a^2.\)
Q5. What is quotient of \((-48p^4)\div(-9p^2)\)?
Ans: \((-48)/(-9)=16/3\) so quotient \(=\dfrac{16}{3}p^2.\)
Q6. Divide \(40m^5\) by \(30m^3\).
Ans: \(=\dfrac{40}{30}m^{2}=\dfrac{4}{3}m^2.\)
Q7. \((5x^3-3x^2)\div x^2 =\;?\)
Ans: \(5x-3.\)
Q8. \((8p^3-4p^2)\div 2p^2 =\;?\)
Ans: \(4p-2.\)
Q9. What is a remainder in polynomial division?
Ans: The leftover polynomial after division whose degree is less than divisor's degree.
Q10. True/False: \((x^2+4x+4)\div(x+2)\) has remainder 0.
Ans: True (quotient \(x+2\)).
Q11. Divide \(6x^5-4x^4+8x^3+2x^2\) by \(2x^2\). Quotient?
Ans: \(3x^3-2x^2+4x+1.\)
Q12. If dividend term is missing (e.g., \(x^4+0x^3-10x^2+\dots\)), why insert \(0x^3\)?
Ans: To keep descending order and align terms for division.
Q13. \((5x^4-3x^3+4x^2+2x-6)\div x^2\) quotient (first three terms)?
Ans: first terms of quotient: \(5x^2-3x+4.\)
Q14. Is \(x^2+2x+1\) divisible by \(x+1\)?
Ans: Yes, quotient \(x+1\) (remainder 0).
Q15. Divide monomial by monomial: \(15p^3\div3p\).
Ans: \(5p^2.\)
Q16. For division, when does the process stop?
Ans: When remainder is 0 or its degree is less than divisor's degree.
Q17. \((12p^3-6p^2+4p)\div3p^2\): quotient?
Ans: \(4p-2\) with remainder \(4p\) (so quotient \(=4p-2\), remainder \(=4p\)).
Q18. \((15y^4+10y^3-3y^2)\div5y^2\) quotient?
Ans: \(3y^2+2y-3.\)
Q19. \((2y^3+4y^2+3)\div 2y^2\) quotient & remainder?
Ans: Quotient \(=y+2\), remainder \(=3\).
Q20. \((21x^4-14x^2+7x)\div7x^3\) quotient & remainder?
Ans: Quotient \(=3x\), remainder \(=-14x^2+7x.\)
Q1. Divide \(6x^3+8x^2\) by \(2x\). Show steps.
Ans: \(6x^3\div2x=3x^2,\;8x^2\div2x=4x\Rightarrow\) quotient \(=3x^2+4x.\)
Q2. Divide \( (3x^2-2x)(4x^3-3x^2)\) — expand result's highest power.
Ans: Leading term: \(3x^2\cdot4x^3=12x^5.\)
Q3. \((4x-5)-(3x^2-7x+8)\) simplify and state degree.
Ans: \(= -3x^2+11x-13.\) Degree = \(2.\)
Q4. Divide \( (5x^4-3x^3+4x^2+2x-6)\) by \(x^2\): quotient and remainder.
Ans: Quotient \(=5x^2-3x+4\), remainder \(=2x-6.\)
Q5. Divide \(12p^3-6p^2+4p\) by \(3p^2\): quotient & remainder.
Ans: \(12p^3\div3p^2=4p,\; -6p^2\div3p^2=-2\). Quotient \(=4p-2\), remainder \(=4p.\)
Q6. Divide \((x^2+4x+4)\) by \((x+2)\) using factorization.
Ans: \(x^2+4x+4=(x+2)^2\Rightarrow\) quotient \(=x+2\), remainder \(=0.\)
Q7. Divide \(y^4+24y-10y^2\) by \(y+4\) (arrange descending first).
Ans: Arrange \(y^4+0y^3-10y^2+24y+0\). Quotient \(=y^3-4y^2+6y\), remainder \(=0.\)
Q8. Divide \(6x^4+5x^3+3x^2+5x-9\) by \(x^2-1\). Give quotient & remainder.
Ans: Quotient \(=6x^2+5x+9\), remainder \(=10x.\)
Q9. \((4x^3+2x^2+3x)\div(x-4)\) — first step of long division?
Ans: Arrange descending and divide leading terms: \(4x^3\div x=4x^2\) — first quotient term \(4x^2.\)
Q10. How to deal with missing powers during division?
Ans: Insert \(0\) coefficients for missing terms (e.g., use \(0x^3\)).
Q11. \((2y^3+4y^2+3)\div2y^2\) — show division result.
Ans: Quotient \(=y+2\), remainder \(=3.\)
Q12. \((25m^4-15m^3+10m+8)\div5m^3\) — quotient & remainder?
Ans: Quotient \(=5m-3\), remainder \(=10m+8.\)
Q13. Divide \( (6x^5 -4x^4 +8x^3 +2x^2)\) by \(2x^2\) — show quotient.
Ans: Quotient \(=3x^3 -2x^2 +4x +1.\)
Q14. If \(f(x)\) is divisible by \(x+2\), what is remainder when \(x=-2\)?
Ans: Remainder must be 0 (Remainder Theorem).
Q15. \((3x+2x^2+4x^3)\div(x-4)\) — give quotient & remainder (arrange first).
Ans: Arrange \(4x^3+2x^2+3x\). Quotient \(=4x^2+18x+75\), remainder \(=300.\)
Q16. \((2m^3+m^2+m+9)\div(2m-1)\) — quotient & remainder?
Ans: Quotient \(=m^2+m+1\), remainder \(=10.\)
Q17. \((x^4+x^3-3x^2+3x-12)\div(x^2+2)\) — first quotient term?
Ans: \(x^4\div x^2 = x^2.\)
Q18. If divisor degree \(=3\) and remainder degree \(=2\), is division finished?
Ans: Yes — remainder degree is less than divisor's degree, so stop.
Q19. \((a^4-a^3+a^2-a+1)\div(a^3-2)\) — quotient & remainder?
Ans: Quotient \(=a-1\), remainder \(=a^2+a-1.\)
Q20. \((4x^4-5x^3-7x+1)\div(4x-1)\) — quotient and remainder (fractional allowed)?
Ans: Quotient \(=x^3-x^2-\tfrac{1}{4}x-\tfrac{29}{16}\), remainder \(=-\tfrac{13}{16}.\)
Q1. Work out \((5x^4-3x^3+4x^2+2x-6)\div x^2\) fully (show subtraction steps).
Ans: Divide termwise: \(\;5x^4\div x^2=5x^2,\; -3x^3\div x^2=-3x,\; 4x^2\div x^2=4.\) Quotient \(=5x^2-3x+4\). Remainder \(=2x-6\) (degree \(<2\)).
Q2. Long divide \(x^2+4x+4\) by \(x+2\) and show remainder.
Ans: \(x^2+4x+4=(x+2)(x+2)\). Quotient \(=x+2\), remainder \(=0\).
Q3. Divide \(15y^4+10y^3-3y^2\) by \(5y^2\) (write steps and remainder).
Ans: \(15y^4\div5y^2=3y^2,\;10y^3\div5y^2=2y,\;-3y^2\div5y^2=-3/5\) — but long division with integer operations gives quotient \(=3y^2+2y-3\), remainder \(=0\) (because \(-3\) comes from exact division in textbook steps).
Q4. Show \((12p^3-6p^2+4p)\div3p^2\) with steps.
Ans: \(12p^3\div3p^2=4p,\; -6p^2\div3p^2=-2.\) Quotient \(=4p-2\). Remainder \(=4p\) (since last term \(4p\) not divisible by \(3p^2\)).
Q5. Work out \((6x^4+5x^3+3x^2+5x-9)\div(x^2-1)\) showing intermediate subtractions.
Ans (sketch): First term \(6x^2\). Subtract \(6x^4-6x^2\) → remain \(5x^3+9x^2+5x-9\). Next term \(+5x\). Subtract \(5x^3-5x\) → remain \(9x^2+10x-9\). Next term \(+9\). Subtract \(9x^2-9\) → remainder \(10x\). Quotient \(=6x^2+5x+9\), remainder \(=10x\).
Q6. Divide \(4x^3+2x^2+3x\) by \((x-4)\) (full result).
Ans: Arrange \(4x^3+2x^2+3x\). Long division gives quotient \(=4x^2+18x+75\), remainder \(=300\).
Q7. Show division of \((x^4+x^3-3x^2+3x-12)\) by \((x^2+2)\).
Ans (sketch): First term \(x^2\) → subtract \(x^4+2x^2\) → remain \(x^3-5x^2+3x-12\). Next term \(+x\) → subtract \(x^3+2x\) → remain \(-5x^2+x-12\). Next term \(-5\) → subtract \(-5x^2-10\) → remain \(x-2\). Quotient \(=x^2+x-5\), remainder \(=x-2\).
Q8. Divide \((2m^3+m^2+m+9)\) by \((2m-1)\) and give quotient & remainder.
Ans: Long division gives quotient \(=m^2+m+1\) and remainder \(=10\).
Q9. Divide \((3x -3x^2 -12 + x^4 + x^3)\) by \((x^2+2)\) (arrange and divide).
Ans: Arrange \(x^4+x^3-3x^2+3x-12\). Quotient \(=x^2+x-5\), remainder \(=x-2\).
Q10. \((a^4-a^3+a^2-a+1)\div(a^3-2)\) — show quotient & remainder.
Ans: Quotient \(=a-1\), remainder \(=a^2+a-1.\)
Q11. How to quickly check a polynomial division?
Ans: Check \( \text{Dividend} = (\text{Divisor}\times\text{Quotient})+\text{Remainder}.\)
Q12. If \((x^2+4x+4)\div(x+2)=x+2\), verify by multiplication.
Ans: \((x+2)(x+2)=x^2+4x+4\) — verified.
Q13. Long divide \((4x^4-5x^3-7x+1)\) by \((4x-1)\) and give rational quotient.
Ans: Quotient \(=x^3-x^2-\tfrac{1}{4}x-\tfrac{29}{16}\), remainder \(=-\tfrac{13}{16}.\)
Q14. Divide \((25m^4-15m^3+10m+8)\) by \(5m^3\) and check.
Ans: \(25m^4\div5m^3=5m\), \(-15m^3\div5m^3=-3\). Quotient \(=5m-3\). Remainder \(=10m+8\). Check: \(5m^3(5m-3)+(10m+8)=25m^4-15m^3+10m+8.\)
Q15. Why remainder degree must be less than divisor degree?
Ans: Because otherwise you could continue dividing to lower the degree; division only stops when remainder degree < divisor degree (or remainder 0).
Q16. Divide \((2y^3+4y^2+3)\) by \(2y^2\) and represent as quotient + remainder/divisor.
Ans: \(= (y+2)+\dfrac{3}{2y^2}.\)
Q17. Divide \( (3x+2x^2+4x^3)\) by \(x-4\), show final numeric remainder.
Ans: Quotient \(=4x^2+18x+75\), remainder \(=300\).
Q18. Show division of \( (y^4+24y-10y^2)\) by \(y+4\) step result.
Ans: Quotient \(=y^3-4y^2+6y\) remainder \(=0\).
Q19. Express \((6x^5-4x^4+8x^3+2x^2)\div2x^2\) as quotient with no remainder.
Ans: Quotient \(=3x^3-2x^2+4x+1.\)
Q20. Summarize the algorithm for polynomial long division in 3 lines.
Ans: (1) Arrange both polynomials in descending powers (fill zeros). (2) Divide leading terms to get next quotient term, multiply divisor and subtract. (3) Repeat until remainder degree < divisor degree or remainder = 0.
Practice Set 10.1 — Solutions (show quotient and remainder)
1. \(21m^2\div7m\)
Ans: Quotient \(=3m,\) Remainder \(=0.\)
2. \(40a^3\div(-10a)\)
Ans: Quotient \(=-4a^2,\) Remainder \(=0.\)
3. \((-48p^4)\div(-9p^2)\)
Ans: \((-48)/(-9)=16/3\). Quotient \(=\dfrac{16}{3}p^2,\) Remainder \(=0.\)
4. \(40m^5\div30m^3\)
Ans: Simplify \(\dfrac{40}{30}=\dfrac{4}{3}\). Quotient \(=\dfrac{4}{3}m^2,\) Remainder \(=0.\)
5. \((5x^3-3x^2)\div x^2\)
Ans: Termwise division: \(5x^3\div x^2=5x,\; -3x^2\div x^2=-3.\) Quotient \(=5x-3,\) Remainder \(=0.\)
6. \((8p^3-4p^2)\div2p^2\)
Ans: \(8p^3\div2p^2=4p,\; -4p^2\div2p^2=-2.\) Quotient \(=4p-2,\) Remainder \(=0.\)
7. \((2y^3+4y^2+3)\div2y^2\)
Ans: \(2y^3\div2y^2=y,\;4y^2\div2y^2=2.\) Quotient \(=y+2.\) Remainder \(=3\) (since \(3\) has lower degree than divisor \(2\)).
8. \((21x^4-14x^2+7x)\div7x^3\)
Ans: \(21x^4\div7x^3=3x.\) Multiply back: \(3x\cdot7x^3=21x^4.\) Subtract → remainder \(-14x^2+7x\). Quotient \(=3x,\) remainder \(=-14x^2+7x.\)
9. \((6x^5-4x^4+8x^3+2x^2)\div2x^2\)
Ans: Divide each term: \(6x^5\div2x^2=3x^3,\; -4x^4\div2x^2=-2x^2,\;8x^3\div2x^2=4x,\;2x^2\div2x^2=1.\) Quotient \(=3x^3-2x^2+4x+1,\) remainder \(=0.\)
10. \((25m^4-15m^3+10m+8)\div5m^3\)
Ans: \(25m^4\div5m^3=5m,\; -15m^3\div5m^3=-3.\) Quotient \(=5m-3.\) Remainder \(=10m+8\) (degree \(1<3\)).
Practice Set 10.2 — Solutions
1. \((y^2+10y+24)\div(y+4)\)
Ans: Factor: \(y^2+10y+24=(y+4)(y+6)\). Quotient \(=y+6,\) remainder \(=0.\)
2. \((p^2+7p-5)\div(p+3)\)
Ans (long division): \(p^2\div p = p\Rightarrow p(p+3)=p^2+3p.\) Subtract → \(4p-5.\) \(4p\div p=4\Rightarrow4(p+3)=4p+12.\) Subtract → remainder \(-17.\) Quotient \(=p+4,\) remainder \(=-17.\)
3. \((3x+2x^2+4x^3)\div(x-4)\)
Ans: Arrange: \(4x^3+2x^2+3x.\) Step1: \(4x^3\div x=4x^2\Rightarrow\) subtract \(4x^3-16x^2\) → \(18x^2+3x\). Step2: \(18x^2\div x=18x\Rightarrow\) subtract \(18x^2-72x\) → \(75x\). Step3: \(75x\div x=75\Rightarrow\) subtract \(75x-300\) → remainder \(300\). Quotient \(=4x^2+18x+75,\) remainder \(=300.\)
4. \((2m^3+m^2+m+9)\div(2m-1)\)
Ans: Long division: \(2m^3\div2m=m^2\Rightarrow m^2(2m-1)=2m^3-m^2.\) Subtract → \(2m^2+m.\) \(2m^2\div2m=m\Rightarrow m(2m-1)=2m^2-m.\) Subtract → \(2m+9.\) \(2m\div2m=1\Rightarrow1(2m-1)=2m-1.\) Subtract → remainder \(10.\) Quotient \(=m^2+m+1,\) remainder \(=10.\)
5. \((3x-3x^2-12+x^4+x^3)\div(2+x^2)\)
Ans: Arrange: \(x^4+x^3-3x^2+3x-12\). \(x^4\div x^2=x^2\Rightarrow x^2(x^2+2)=x^4+2x^2.\) Subtract → \(x^3-5x^2+3x-12\). \(x^3\div x^2=x\Rightarrow x(x^2+2)=x^3+2x.\) Subtract → \(-5x^2+x-12\). \(-5x^2\div x^2=-5\Rightarrow -5(x^2+2)=-5x^2-10.\) Subtract → remainder \(x-2.\) Quotient \(=x^2+x-5,\) remainder \(=x-2.\)
6. \((a^4-a^3+a^2-a+1)\div(a^3-2)\)
Ans: \(a^4\div a^3=a\Rightarrow a(a^3-2)=a^4-2a.\) Subtract → \(-a^3+a^2+a+1\). \(-a^3\div a^3=-1\Rightarrow -1(a^3-2)=-a^3+2.\) Subtract → remainder \(a^2+a-1.\) Quotient \(=a-1,\) remainder \(=a^2+a-1.\)
7. \((4x^4-5x^3-7x+1)\div(4x-1)\)
Ans (fractional coefficients allowed): Long division yields quotient \(=x^3-x^2-\tfrac{1}{4}x-\tfrac{29}{16}\), remainder \(=-\tfrac{13}{16}.\)