(9y-2)(2.1-7y)=0

Solution for (9y-2)(2.1-7y)=0 equation:

(9y-2)(2.1-7y)=0

We add all the numbers together, and all the variables

(9y-2)(-7y+2.1)=0

We multiply parentheses ..

(-63y^2+18.9y+14y-4.2)=0

We get rid of parentheses

-63y^2+18.9y+14y-4.2=0

We add all the numbers together, and all the variables

-63y^2+32.9y-4.2=0

a = -63; b = 32.9; c = -4.2;
Δ = b2-4ac
Δ = 32.92-4·(-63)·(-4.2)
Δ = 24.01
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(32.9)-\sqrt{24.01}}{2*-63}=\frac{-32.9-\sqrt{24.01}}{-126}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(32.9)+\sqrt{24.01}}{2*-63}=\frac{-32.9+\sqrt{24.01}}{-126}
$