Question 621573
{{{ 8x^2 + 28x = 36 }}}
Divide both sides by {{{ 4 }}}
{{{ 2x^2 + 7x = 9 }}}
Divide both sides by {{{ 2 }}}
{{{ x^2 + (7/2)*x = 9/2 }}}
I will complete the square
{{{ x^2 + (7/2)*x + (7/4)^2 = 72/16 + (7/4)^2 }}}
{{{ ( x + 7/4 )^2  = 72/16 + 49/16 }}}
{{{ ( x + 7/4 )^2 = 121/16 }}}
{{{ ( x + 7/4 )^2 = (11/4)^2 }}}
Take the square root of both sides
{{{ x + 7/4 = 11/4 }}}
{{{ x = 11/4 - 7/4 }}}
{{{ x = 1 }}}
and also,
{{{ x + 7/4 = -11/4 }}}
{{{ x = -9/2 }}}
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I'll check the 2nd answer:
{{{ 8x^2 + 28x = 36 }}}
{{{ 8*(-9/2)^2 + 28*(-9/2) = 36 }}}
{{{ 8*(81/4) - 252/2 = 36 }}}
{{{ 162 - 126 = 36 }}}
{{{ 36 = 36 }}}
OK