(5u-7)(u+9)=0

Solution for (5u-7)(u+9)=0 equation:

(5u-7)(u+9)=0

We multiply parentheses ..

(+5u^2+45u-7u-63)=0

We get rid of parentheses

5u^2+45u-7u-63=0

We add all the numbers together, and all the variables

5u^2+38u-63=0

a = 5; b = 38; c = -63;
Δ = b2-4ac
Δ = 382-4·5·(-63)
Δ = 2704
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2704}=52$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(38)-52}{2*5}=\frac{-90}{10}
=-9
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(38)+52}{2*5}=\frac{14}{10}
=1+2/5
$