0=21y^2+11y-2

Solution for 0=21y^2+11y-2 equation:

0=21y^2+11y-2

We move all terms to the left:

0-(21y^2+11y-2)=0

We add all the numbers together, and all the variables

-(21y^2+11y-2)=0

We get rid of parentheses

-21y^2-11y+2=0

a = -21; b = -11; c = +2;
Δ = b2-4ac
Δ = -112-4·(-21)·2
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-11)-17}{2*-21}=\frac{-6}{-42}
=1/7
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-11)+17}{2*-21}=\frac{28}{-42}
=-2/3
$