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3x2 + 9x – 2 for x = -53

 Jul 28, 2016
 #1
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Solve for x:
3 x^2+9 x-2 = 0

Divide both sides by 3:
x^2+3 x-2/3 = 0

Add 2/3 to both sides:
x^2+3 x = 2/3

Add 9/4 to both sides:
x^2+3 x+9/4 = 35/12

Write the left hand side as a square:
(x+3/2)^2 = 35/12

Take the square root of both sides:
x+3/2 = sqrt(35/3)/2 or x+3/2 = -sqrt(35/3)/2

Subtract 3/2 from both sides:
x = sqrt(35/3)/2-3/2 or x+3/2 = -sqrt(35/3)/2

Subtract 3/2 from both sides:
Answer: | x = sqrt(35/3)/2-3/2    or     x = -3/2-sqrt(35/3)/2

 Jul 28, 2016
 #2
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3x2 + 9x – 2 for x = -53

 

3*(-53)^2 + 9*(-53) - 2   [Is this what you wanted?]

8,427        + ( -477) - 2

8,427 - 477 - 2

=   7,948

 Jul 28, 2016

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