-21=29p-10p^2

Solution for -21=29p-10p^2 equation:

-21=29p-10p^2

We move all terms to the left:

-21-(29p-10p^2)=0

We get rid of parentheses

10p^2-29p-21=0

a = 10; b = -29; c = -21;
Δ = b2-4ac
Δ = -292-4·10·(-21)
Δ = 1681
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$p_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$p_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1681}=41$
$p_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-29)-41}{2*10}=\frac{-12}{20}
=-3/5
$
$p_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-29)+41}{2*10}=\frac{70}{20}
=3+1/2
$