15t2-15-90=0

Solution for 15t2-15-90=0 equation:

15t^2-15-90=0

We add all the numbers together, and all the variables

15t^2-105=0

a = 15; b = 0; c = -105;
Δ = b2-4ac
Δ = 02-4·15·(-105)
Δ = 6300
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{6300}=\sqrt{900*7}=\sqrt{900}*\sqrt{7}=30\sqrt{7}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-30\sqrt{7}}{2*15}=\frac{0-30\sqrt{7}}{30}
=-\frac{30\sqrt{7}}{30}
=-\sqrt{7}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+30\sqrt{7}}{2*15}=\frac{0+30\sqrt{7}}{30}
=\frac{30\sqrt{7}}{30}
=\sqrt{7}
$