Question

Question For the function f(x) = 18x^2+ 15x - 10, find a when f(x) = 15.

Answer 1

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:

$x=\frac{-b\pm\sqrt[]{b^2-4ac}}{2a}$

where a= 18, b= 15 and c= -25 and replacing we got:

$x=\frac{-15\pm\sqrt[]{15^2-4\cdot18\cdot(-25)}}{2\cdot18}$

And then the two solutiona are:

x= 5/6

x= -5/3