(7t+9)(t+8)=0

Solution for (7t+9)(t+8)=0 equation:

(7t+9)(t+8)=0

We multiply parentheses ..

(+7t^2+56t+9t+72)=0

We get rid of parentheses

7t^2+56t+9t+72=0

We add all the numbers together, and all the variables

7t^2+65t+72=0

a = 7; b = 65; c = +72;
Δ = b2-4ac
Δ = 652-4·7·72
Δ = 2209
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2209}=47$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(65)-47}{2*7}=\frac{-112}{14}
=-8
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(65)+47}{2*7}=\frac{-18}{14}
=-1+2/7
$