quadratic equations

Question

Select the approximate values of x that are solutions to f(x) = 0, where
f(x) = -2x2 + 8x + 7.

 

The four options are:

{4.74, –0.74}

{-2, 8}

{–4.00, –3.50}

{–0.29, 1.14}

Answer 1

Hi Stepanie,

 

You can do this by just putting the numbers where x is and calculating the numbers

 

f(4.74)=-2(4.74)(4.74)+8(4.74)+7=-44.9352+37.92+7=(approximately) = 0

 

f(–0.74)=-2(–0.74)(–0.74)+8(–0.74)+7=0 approximately

 

You can just try out the rest for practice, and see that they are not the right choices, basically using the same method that I just used.