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

Question

A:{0.56,0.79}

B:{-9,2}

C:{-0.22,-0.44}

D:{-2.25,0.50}

Answer 1

-9x²+2x+4=0      

 Solve using the quadratic formula.

a = -9, b = 2, c = 4

x = -b+√b²-4ac      b²-4ac is all under the square root

             2a

x = -2 + √2²-4(-9)(4)

               2(-9)

x = -2 + √4 + 144

                 -18

x = -2 + √148  = -2 + √4(37)

              -18                -18

x = -2 + 2√37  = -1 + √37

            -18                -9

x = -1 + 6.08276 ≈ .56       and

               -9

x = -1 - 6.08276 ≈  .79

                -9

 

Choice A is the correct one.