9x^2-21x+9=9

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Solution for 9x^2-21x+9=9 equation:



9x^2-21x+9=9
We move all terms to the left:
9x^2-21x+9-(9)=0
We add all the numbers together, and all the variables
9x^2-21x=0
a = 9; b = -21; c = 0;
Δ = b2-4ac
Δ = -212-4·9·0
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-21}{2*9}=\frac{0}{18} =0 $
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+21}{2*9}=\frac{42}{18} =2+1/3 $

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