f(x)=x^3-5x^2-x+6

Question

use synthetic substitution to find f(2) and f(-1) for each function.

Answer 1

f ( x ) = x³ - 5 x ²- x + 6.

1)  f (2 ) = 2³ - 5 * 2 ²- 2 + 6.

f (2 ) = 8 - 20 - 2 + 6.

f (2 ) = 14 - 22 = - 8

f (2 ) = - 8

 f ( x ) = x³ - 5 x ²- x + 6.

2)  f (- 1 ) = ( - 1 )³ - 5 *(- 1)²-( - 1 ) + 6.

f (- 1 ) = - 1 - 5 + 1 + 6.

f (- 1 ) = - 6  + 7 = 1.

f (- 1 ) = 1.

Therefore f (2 ) = - 8 and f (- 1 )  = 1.