7=-16x^2+70x+3

Solution for 7=-16x^2+70x+3 equation:

7=-16x^2+70x+3

We move all terms to the left:

7-(-16x^2+70x+3)=0

We get rid of parentheses

16x^2-70x-3+7=0

We add all the numbers together, and all the variables

16x^2-70x+4=0

a = 16; b = -70; c = +4;
Δ = b2-4ac
Δ = -702-4·16·4
Δ = 4644
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{4644}=\sqrt{36*129}=\sqrt{36}*\sqrt{129}=6\sqrt{129}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-70)-6\sqrt{129}}{2*16}=\frac{70-6\sqrt{129}}{32}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-70)+6\sqrt{129}}{2*16}=\frac{70+6\sqrt{129}}{32}
$