(25-t)(t-15)=0

Solution for (25-t)(t-15)=0 equation:

(25-t)(t-15)=0

We add all the numbers together, and all the variables

(-1t+25)(t-15)=0

We multiply parentheses ..

(-1t^2+15t+25t-375)=0

We get rid of parentheses

-1t^2+15t+25t-375=0

We add all the numbers together, and all the variables

-1t^2+40t-375=0

a = -1; b = 40; c = -375;
Δ = b2-4ac
Δ = 402-4·(-1)·(-375)
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-10}{2*-1}=\frac{-50}{-2}
=+25
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+10}{2*-1}=\frac{-30}{-2}
=+15
$