Question

The polynomial f(x) = x³+ 15x²+ 9x – a when divided by (x + 4) leaves a remainder -80, find the value of a.

Answer 1

Put x = -4

- 64 + 240 - 36 - a = -80

140 - a = -80

a = 220

Answer 2

Heya mate !!! Your answer =>

x + 4 = 0

x = - 4

so....

${x}^{3} + 15 {x}^{2} + 9x - a = -80\\ \\ {( - 4)}^{3} + 15 {( - 4)}^{2} + 9( - 4) - a = -80 \\ \\ - 64 + 240 - 36 - a = -80\\ \\ - 100 + 240 - a= -80\\ \\ 140 - a = 80\\ \\ - a = -80 - 140 \\ \\ - a = - 220 \\ \\ a = 220$

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