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3x squared -42x+9=-5 for completing the square

User BinaryLV
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1 Answer

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3x^2 -42x + 9 = -5

Subtract 9 from both sides

3x^2 -42x = -5 - 9


3x^2 -42x = -14

Divide by 3 through

x^2 -14x = - (14)/(3)

Add (b/2)^2 to form perfect square

x^2 -14x + ((14)/(2))^2 = - (14)/(3) + ((14)/(2))^2

Form perfect square

(x -7)^2 = (7)/(3)

square root both sides

(x -7) = \pm \sqrt{(7)/(3)}

Add 7 to both sides

x = \pm \sqrt{(7)/(3)} + 7

Rewrite the answer into 2 different answers

x = 7 + \sqrt{(7)/(3)} \ or \ 7 - \sqrt{(7)/(3)}




User Mayank Sharma
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