30y^2-25=9y^2

Solution for 30y^2-25=9y^2 equation:

30y^2-25=9y^2

We move all terms to the left:

30y^2-25-(9y^2)=0

We add all the numbers together, and all the variables

21y^2-25=0

a = 21; b = 0; c = -25;
Δ = b2-4ac
Δ = 02-4·21·(-25)
Δ = 2100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{2100}=\sqrt{100*21}=\sqrt{100}*\sqrt{21}=10\sqrt{21}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-10\sqrt{21}}{2*21}=\frac{0-10\sqrt{21}}{42}
=-\frac{10\sqrt{21}}{42}
=-\frac{5\sqrt{21}}{21}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+10\sqrt{21}}{2*21}=\frac{0+10\sqrt{21}}{42}
=\frac{10\sqrt{21}}{42}
=\frac{5\sqrt{21}}{21}
$