3p^2-3p-21=7+2p^2

Solution for 3p^2-3p-21=7+2p^2 equation:

3p^2-3p-21=7+2p^2

We move all terms to the left:

3p^2-3p-21-(7+2p^2)=0

We get rid of parentheses

3p^2-2p^2-3p-7-21=0

We add all the numbers together, and all the variables

p^2-3p-28=0

a = 1; b = -3; c = -28;
Δ = b2-4ac
Δ = -32-4·1·(-28)
Δ = 121
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$p_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$p_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{121}=11$
$p_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-11}{2*1}=\frac{-8}{2}
=-4
$
$p_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+11}{2*1}=\frac{14}{2}
=7
$