Question

Working Out function

The function f is defined by:f(x)=x squared+ax+b

it's known that f(0)=7 and f(-2)=17

find values of a and b

A=
B=​

Answer 1

a = -3, b = 7

Explanation:

f(x) just means function in x. y= anything x is just a function in x.

so f(x) = y.

y = x² + ax + b

f(0) = 7 = x² + ax + b

= (0)² + a (0) + b

= b.

b = 7.

f(-2) = 17 = x² + ax + b

= (-2)² + a(-2) + 7

= 4 - 2a + 7

= 11 - 2a

17 - 11 = - 2a

6 = -2a

a = - 6/2

= - 3

a = -3