8x2+22x=21

Solution for 8x2+22x=21 equation:

8x^2+22x=21

We move all terms to the left:

8x^2+22x-(21)=0

a = 8; b = 22; c = -21;
Δ = b2-4ac
Δ = 222-4·8·(-21)
Δ = 1156
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1156}=34$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(22)-34}{2*8}=\frac{-56}{16}
=-3+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(22)+34}{2*8}=\frac{12}{16}
=3/4
$