-12=3(u+5)6u

Solution for -12=3(u+5)6u equation:

-12=3(u+5)6u

We move all terms to the left:

-12-(3(u+5)6u)=0


We calculate terms in parentheses: -(3(u+5)6u), so:

3(u+5)6u

We multiply parentheses

18u^2+90u

Back to the equation:

-(18u^2+90u)


We get rid of parentheses

-18u^2-90u-12=0

a = -18; b = -90; c = -12;
Δ = b2-4ac
Δ = -902-4·(-18)·(-12)
Δ = 7236
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{7236}=\sqrt{36*201}=\sqrt{36}*\sqrt{201}=6\sqrt{201}$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-90)-6\sqrt{201}}{2*-18}=\frac{90-6\sqrt{201}}{-36}
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-90)+6\sqrt{201}}{2*-18}=\frac{90+6\sqrt{201}}{-36}
$