k(k+3)=3k+81

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Solution for k(k+3)=3k+81 equation:



k(k+3)=3k+81
We move all terms to the left:
k(k+3)-(3k+81)=0
We multiply parentheses
k^2+3k-(3k+81)=0
We get rid of parentheses
k^2+3k-3k-81=0
We add all the numbers together, and all the variables
k^2-81=0
a = 1; b = 0; c = -81;
Δ = b2-4ac
Δ = 02-4·1·(-81)
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-18}{2*1}=\frac{-18}{2} =-9 $
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+18}{2*1}=\frac{18}{2} =9 $

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