f(x)=0 where -9x^2+5x+5

Question

Select the approximate values of x that are solutions to this f(x)=0 where f(x)=-9x^2+5x+5

 

Answer 1

Anthony,

 

Just use the quadratic formula to solve ax² + bx + c =0.  In your case a = -9; b = +5; c = +5.

 

The solutions are: x = [-b  +-√(b² - 4ac)]2a = [-5 +-√(25 - 4(-9)(5))]/2(-9)  =  [-5 +-√(205]/(-18)

x = [-5 +-√(205]/(-18) = [-5 +-14.3178]/(-18)

So x1 = [-5 +14.3178]/(-18) = 9.3178/(-18) =    - 0.5177, and the other case 

     x2 = [-5 - 14.3178]/(-18) = -19.3178/(-18) = +1.0732