Question 641789
Do it like this one.
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4x^2+12x-7=0
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Divide by a, the coeffient of x^2
{{{x^2 + 3x = 7/4}}}
c = (b/2)^2 = (3/2)^2 = 9/4
Add c to both sides
{{{x^2 + 3x + 9/4 = 16/4}}}
{{{(x + 3/2)^2 = 4}}}
x + 3/2 = ± 2
x = -3/2 ± 2