How do you solve $0.9x - 0.7x^2 = -1$ using the quadratic formula?

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Answer 1 · 2017-04-04T00:38:37

I got: $-5/7 and 2$

We can first multiply by $10$ and write it in the form: $ax^2+bx+c=0$ :

so:
$10*(0.9x-0.7x^2)=10*(-1)$

$9x-7x^2=-10$

$-7x^2+9x+10=0$

$x_(1,2)=(-9+-sqrt(81-4(-7*10)))/-14=(-9+-sqrt(361))/-14=(-9+-19)/-14$

$x_1=(-9+19)/-14=-10/14=-5/7$
$x_2=(-9-19)/-14=28/14=2$

How do you solve 0.9x - 0.7x^2 = -1 0.9x - 0.7x^2 = -1 using the quadratic formula?