Question

If f(x)=9-4x^2 Find
a) f(-2)
b) f(-3) f(3)
c) x such that f(x) = 0​

Answer 1

see explanation

Explanation:

(a)

To evaluate f(- 2) substitute x = - 2 into f(x) , that is

f(- 2) = 9 - 4(- 2)² = 9 - 4(4) = 9 - 16 = - 7

(b)

Similarly substitute x = - 3 and x = 3 into f(x)

f(- 3) = 9 - 4(- 3)² = 9 - 4(9) = 9 - 36 = - 27

f(3) = 9 - 4(3)² = 9 - 4(9) = 9 - 36 = - 27

(c)

let f(x) = 0 , then

9 - 4x² = 0 ( add 4x² to both sides )

9 = 4x² ( divide both sides by 4 )

`(9)/(4)` = x² ( take the square root of both sides )

±
`\sqrt{(9)/(4) }` = x

±
`(√(9) )/(√(4) )` = x

±
`(3)/(2)` = x

That is x = -
`(3)/(2)` or x =
`(3)/(2)`