Select the approximate values of x that are solutions to f(x) = 0, where f(x) = -9x^2 + 4x + 9.

Question

A{–1.00, 0.44}

B{-9, 4}

C{–0.44, –1.00}

D{–0.80, 1.25}

Answer 1

0 = -9x² + 4x + 9

 

Use the quadratic formula:

 

x = (4/18) ± (1/18)√(4²-4(-9)(9))

x = 2/9 ± (1/18)√340

x ≅ -0.8 and 1.25

 

Looks like D is the answer.