SOLUTION: Use the method of completing the square to solve the equation 3 = 2x2 + 8x

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Question 408892: Use the method of completing the square to solve the equation 3 = 2x2 + 8x
Found 2 solutions by nerdybill, ewatrrr:
Answer by nerdybill(7384)   (Show Source): You can put this solution on YOUR website!
3 = 2x^2 + 8x
3 = 2(x^2 + 4x)
3+8 = 2(x^2 + 4x + 4)
11 = 2(x+2)^2
11/2 = (x+2)^2
sqrt(11/2) = x+2
sqrt(11/2) - 2 = x
.345 = x


Answer by ewatrrr(24785)   (Show Source): You can put this solution on YOUR website!


Hi

Using the method of completing the square to solve the equation:

2x^2 + 8x = 3    |note the use of the ^ (uppercase 6)

(x^2+4x) = 3/2

(x+2)^2 -4 = 3/2

 (x+2)^2 = 11/2

   x+2 = ħ sqrt(5.5)

    x = -2 ħsqrt(5.5)

    x = {0.345207879911715, -4.34520787991172}

CHECKING our Answer*** with the Quadratic Formula

2x^2 + 8x - 3 = 0





 x = {0.345207879911715, -4.34520787991172} 

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