Solution
For the function f(x) = 18x^2+ 15x - 10, find a when f(x) = 15.
For this case we can do the following:
15 =18x^2+ 15x - 10
We can subtract 15 in both sides and we got:
18x^2 +15x -25=0
And we can apply the quadratic formula given by:
[tex]x=\frac{-b\pm\sqrt[]{b^2-4ac}}{2a}[/tex]where a= 18, b= 15 and c= -25 and replacing we got:
[tex]x=\frac{-15\pm\sqrt[]{15^2-4\cdot18\cdot(-25)}}{2\cdot18}[/tex]And then the two solutiona are:
x= 5/6
x= -5/3
