# Math Help - Find x in quadratic when y=11

1. ## Find x in quadratic when y=11

Hi

I have a quadratic -5x^2 + 15x +1 = 0

I can find x where y=0, (-54.1 or +24.1)

But how do I find x when y = 11

Factorising, completing the square and using the quadratic formula are
all about finding x when y = 0. But what do you do when you want y=
some other value?

Angus

2. $-5x^2 + 15x + 1 = 11$

$-5x^2 + 15x - 10 = 0$

$x^2 - 3x + 2 = 0$

$(x - 1)(x - 2) = 0$

$x -1 = 0$ or $x - 2 = 0$

$x = 1$ or $x = 2$.

3. Why didn't I think of that

Many thanks.