(y-4)(y+2.3)=0

Solution for (y-4)(y+2.3)=0 equation:

(y-4)(y+2.3)=0

We multiply parentheses ..

(+y^2+2.3y-4y-9.2)=0

We get rid of parentheses

y^2+2.3y-4y-9.2=0

We add all the numbers together, and all the variables

y^2-1.7y-9.2=0

a = 1; b = -1.7; c = -9.2;
Δ = b2-4ac
Δ = -1.72-4·1·(-9.2)
Δ = 39.69
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{-(-1.7)-\sqrt{39.69}}{2*1}=\frac{1.7-\sqrt{39.69}}{2}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.7)+\sqrt{39.69}}{2*1}=\frac{1.7+\sqrt{39.69}}{2}
$