Question

When the function f(x) = 2x^n + ax^2 - 6 is divided by (x - 1), the remainder is -7 and when divided by (x + 3), the remainder is 129.

Calculate the value of "a" and "n" and hence write the polynomial function completely.

Answer 1

Explanation:

Answer 2

Explanation:

From the fact that the remainder is -7 after we divide by x -1 , then we know that f(1) = -7. But f(1) = 2 + a - 6.

So 2 + a - 6 = -7

a - 4 = -7

a = 4 - 7

a = -3.

Also we know that when divided by x + 3 the remainder is 129. Hence f( -3) = 129

129 = f(-3) = 2 (-3)^ n + (-3)(-3)^2 -6

129 = 2 (-3)^n -27 - 6

129 = 2 (-3)^n -33

129 + 33 = 2(-3)^n

162 = 2 (-3)^n

81 = (-3)^n

Hence n =4 and therefore f(x) = 2x^4 -3x^2 - 6.