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Given that x+2 and x-3 are factors of x^...

Given that x+2 and x-3 are factors of `x^3+ax+b`, calculate the values of a and b.

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To solve the problem, we need to find the values of \( a \) and \( b \) given that \( x + 2 \) and \( x - 3 \) are factors of the polynomial \( f(x) = x^3 + ax + b \). ### Step-by-Step Solution: 1. **Identify the roots from the factors**: Since \( x + 2 \) and \( x - 3 \) are factors, we can set them to zero to find the roots: \[ x + 2 = 0 \implies x = -2 \] \[ x - 3 = 0 \implies x = 3 \] 2. **Evaluate the polynomial at the roots**: Since both \( x = -2 \) and \( x = 3 \) are roots, we can substitute these values into the polynomial \( f(x) \) and set them equal to zero. For \( x = -2 \): \[ f(-2) = (-2)^3 + a(-2) + b = 0 \] Simplifying this gives: \[ -8 - 2a + b = 0 \quad \text{(Equation 1)} \] Rearranging it: \[ -2a + b = 8 \quad \text{(Equation 1)} \] For \( x = 3 \): \[ f(3) = 3^3 + a(3) + b = 0 \] Simplifying this gives: \[ 27 + 3a + b = 0 \quad \text{(Equation 2)} \] Rearranging it: \[ 3a + b = -27 \quad \text{(Equation 2)} \] 3. **Set up the system of equations**: Now we have the following two equations: \[ -2a + b = 8 \quad \text{(1)} \] \[ 3a + b = -27 \quad \text{(2)} \] 4. **Eliminate \( b \)**: We can eliminate \( b \) by subtracting Equation (1) from Equation (2): \[ (3a + b) - (-2a + b) = -27 - 8 \] This simplifies to: \[ 3a + b + 2a - b = -35 \] \[ 5a = -35 \] Dividing both sides by 5 gives: \[ a = -7 \] 5. **Substitute \( a \) back to find \( b \)**: Now, substitute \( a = -7 \) back into Equation (1): \[ -2(-7) + b = 8 \] Simplifying gives: \[ 14 + b = 8 \] \[ b = 8 - 14 = -6 \] 6. **Final values**: Thus, the values of \( a \) and \( b \) are: \[ a = -7, \quad b = -6 \] ### Summary: The values of \( a \) and \( b \) are: \[ a = -7, \quad b = -6 \]
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ICSE-REMAINDER AND FACTOR THEOREMS-Exercise 8C
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  3. Using Remainder Theorem, factorise : x^(3)+10x^2-37x+26 completely.

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  4. When x^(3)+3x^(2)-mx+4 is divided by x -2, the remainder is m + 3. Fin...

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  5. What should be subtracted from 3x^(3)-8x^(2)+4x - 3, so that the resul...

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  6. If (x + 1) and (x - 2) are factors of x^(3)+ (a + 1)x^2 -(b - 2) x-6, ...

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  7. If x= 2 is a factor of x^2+ ax + b and a +b =1. find the values of a a...

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  8. Factorise x^(3)+6x^(2)+11x+6 completely using factor theorem.

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  9. Find the value of 'm'. If mx^3+ 2x^2- 3 and x^2- mx+ 4 leave the same ...

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  10. The polynomial px^(3)+4x^(2)-3x+q completely divisible by x^2-1: find ...

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  11. Find the number which should be added to x^2+ x +3 so that the resulti...

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  12. When the polynomial x^(3)+2x^(2)-5ax-7 is divided by (x - 1), the rema...

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  13. (3x + 5) is a factor of the polynomial (a-1)x^(3)+(a+1)x^2-(2a+1)x-15....

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  14. When divided by x- 3 the polynomials x^3-px^2+x+6 and 2x^3-x^2-(p+3)x-...

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  15. Use the Remainder Theorem to factorise the following expression 2x^(3)...

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  16. Using remainder theorem, find the value of k if on dividing 2x^3+ 3x^2...

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  17. What must be subtracted from 16x^3- 8x^2+4x+7 so that the resulting ex...

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