(7d-4)(6d+7)=0

Solution for (7d-4)(6d+7)=0 equation:

(7d-4)(6d+7)=0

We multiply parentheses ..

(+42d^2+49d-24d-28)=0

We get rid of parentheses

42d^2+49d-24d-28=0

We add all the numbers together, and all the variables

42d^2+25d-28=0

a = 42; b = 25; c = -28;
Δ = b2-4ac
Δ = 252-4·42·(-28)
Δ = 5329
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5329}=73$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(25)-73}{2*42}=\frac{-98}{84}
=-1+1/6
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(25)+73}{2*42}=\frac{48}{84}
=4/7
$