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## Homework Statement

Find values of k for which (5 + 4x - x^2 = k) has equal roots.

I know the answer is k = 9 but i don't know how to get there..

## Homework Equations

ax^2 + bx + c = 0

Discriminant = b^2 - 4ac

I know the discriminant has to equal 0 for the equation to have equal roots..

## The Attempt at a Solution

But i get Discriminent = 36..?

and the roots equaling -1 or 5..?

Im lost.