(5u-9)(1+u)=0

Solution for (5u-9)(1+u)=0 equation:

(5u-9)(1+u)=0

We add all the numbers together, and all the variables

(5u-9)(u+1)=0

We multiply parentheses ..

(+5u^2+5u-9u-9)=0

We get rid of parentheses

5u^2+5u-9u-9=0

We add all the numbers together, and all the variables

5u^2-4u-9=0

a = 5; b = -4; c = -9;
Δ = b2-4ac
Δ = -42-4·5·(-9)
Δ = 196
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{196}=14$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-14}{2*5}=\frac{-10}{10}
=-1
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+14}{2*5}=\frac{18}{10}
=1+4/5
$