54=x*2x+10*2x-3*x-3*10
54=2x^2+20x-3x-30
54=2x^2+17x-30
2x^2+17x-30-54=0
2x^2+17x-84=0
x^2+8.5x-42=0
to see how to solve quadratic equations see: http://en.wikipedia.org/wiki/Quadratic_equation
formula:
x^2+p*x+q=0
x1=-p/2+sqrt( (p/2)^2-q )
x2=-p/2-sqrt( (p/2)^2-q )
with p=8.5 and q=-42
x1=-12
x2=3.5
54=((x+10)×(2×x−3))={x=−12x=72}
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