Given that p(x)=(x+1)3+5(x−1)2+ax+b\text{p}(x) = (x + 1)^3 + 5(x - 1)^2 + ax + b has a factor x−1x - 1 and it leaves a remainder of 21 when divided by x−2x - 2, find the value of aa and of bb.

Work through it with AI →

It won't just hand you the answer — it asks where you're stuck.How the checker works

Worked solution

1

1. Apply the Factor Theorem to form the first equation

Since x−1x - 1 is a factor, p(1)=0\text{p}(1) = 0.
(1+1)3+5(1−1)2+a(1)+b=0(1 + 1)^3 + 5(1 - 1)^2 + a(1) + b = 0
23+0+a+b=02^3 + 0 + a + b = 0
8+a+b=08 + a + b = 0
a+b=−8— (1)a + b = -8 \quad \text{--- (1)}

2. Apply the Remainder Theorem to form the second equation

Since the remainder is 21 when divided by x−2x - 2, p(2)=21\text{p}(2) = 21.
(2+1)3+5(2−1)2+a(2)+b=21(2 + 1)^3 + 5(2 - 1)^2 + a(2) + b = 21
33+5(1)2+2a+b=213^3 + 5(1)^2 + 2a + b = 21
27+5+2a+b=2127 + 5 + 2a + b = 21
32+2a+b=2132 + 2a + b = 21
2a+b=−11— (2)2a + b = -11 \quad \text{--- (2)}

3. Solve the simultaneous equations to find $a$ and $b$

Subtracting equation (1) from equation (2):
(2a+b)−(a+b)=−11−(−8)(2a + b) - (a + b) = -11 - (-8)
a=−3a = -3

Substitute a=−3a = -3 into equation (1):
−3+b=−8-3 + b = -8
b=−5b = -5

Answer

a=−3a = -3, b=−5b = -5

AI analysis — may contain mistakes.

Worked this one out on paper? Snap your steps and Gigle's AI math checker will circle the step where it went wrong.

More questions on this topic

  1. 1The expression f(x)=ax3+(a−3b)x2+3bx+cf(x) = ax^3 + (a - 3b)x^2 + 3bx + c is exactly divisible by x2+3xx^2 + 3x. When f(x)f(x) is divided by x+2x + 2…
  2. 2The equation of a curve is y=16−ax−x2y=16-ax-x^{2}, where aa is positive constant. Given that yy can be expressed in the form…
  3. 3Show that 1 is a solution of the equation x3−5x2=2−6xx^3 - 5x^2 = 2 - 6x. Hence solve the equation x3−5x2=2−6xx^3 - 5x^2 = 2 - 6x complete…
  4. 4It is given that f(x)=x3+ax2+bx+5f(x)=x^3+ax^2+bx+5, where aa and bb are constants, has a factor of x−1x-1 and leaves a remainder of…
  5. 5It is given that 2x×32(2x)8x+1=9(52x)−52x+15x−5x−1\frac{2^x \times 32(2^x)}{8^{x+1}} = \frac{9(5^{2x}) - 5^{2x+1}}{5^x - 5^{x-1}}. Evaluate 10x10^x with…