0=-5(3y+21)y=

Solution for 0=-5(3y+21)y= equation:

0=-5(3y+21)y=

We move all terms to the left:

0-(-5(3y+21)y)=0

We add all the numbers together, and all the variables

-(-5(3y+21)y)=0


We calculate terms in parentheses: -(-5(3y+21)y), so:

-5(3y+21)y

We multiply parentheses

-15y^2-105y

Back to the equation:

-(-15y^2-105y)


We get rid of parentheses

15y^2+105y=0

a = 15; b = 105; c = 0;
Δ = b2-4ac
Δ = 1052-4·15·0
Δ = 11025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{11025}=105$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(105)-105}{2*15}=\frac{-210}{30}
=-7
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(105)+105}{2*15}=\frac{0}{30}
=0
$