0.3y*(y+1)=10.8

Solution for 0.3y*(y+1)=10.8 equation:

0.3y(y+1)=10.8

We move all terms to the left:

0.3y(y+1)-(10.8)=0

We add all the numbers together, and all the variables

0.3y(y+1)-10.8=0

We multiply parentheses

0y^2+0y-10.8=0

We add all the numbers together, and all the variables

y^2+y-10.8=0

a = 1; b = 1; c = -10.8;
Δ = b2-4ac
Δ = 12-4·1·(-10.8)
Δ = 44.2
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-\sqrt{44.2}}{2*1}=\frac{-1-\sqrt{44.2}}{2}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{44.2}}{2*1}=\frac{-1+\sqrt{44.2}}{2}
$