approximate values of x

Question

Select the approximate values of x that are solution to f(x)=0, where f(x) p= -4x^2+6x+5

 

A) {-0.80, 1.20}

 

B) {-4, 6}

 

C) {-1.50,-1.25}

 

D) {-0.60, 2.10}

Answer 1

                                      

Using the quadratic formula x = -b ± √b²  - 4 

                                                       2a

 

For p= -4x²+6x+5

 a=-4, b=6, c =5

 

Then, putting this all into formula:

 

x= -(6)±√(6)² - 4(-4)(5) = -6±√36 + 80 = -6±√116  ≈ -0.596, 2.096 ≈ -0.60, 2.10

                 2(-4)                       -8                -8

           

Answer 2

use the quadratic formula

 

(-6+√36+80)/(-8)

(-6+√116)/(-8)

(-6+10.77)/(-8)

-16.77/(-8)=2.096≈2.10

4.77/(-8)=-0.596≈-0.60

D. is the answer