Solve for x
x=-40
x=75
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1.5x^{2}-52.5x-4500=0
All equations of the form ax^{2}+bx+c=0 can be solved using the quadratic formula: \frac{-b±\sqrt{b^{2}-4ac}}{2a}. The quadratic formula gives two solutions, one when ± is addition and one when it is subtraction.
x=\frac{-\left(-52.5\right)±\sqrt{\left(-52.5\right)^{2}-4\times 1.5\left(-4500\right)}}{2\times 1.5}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 1.5 for a, -52.5 for b, and -4500 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{-\left(-52.5\right)±\sqrt{2756.25-4\times 1.5\left(-4500\right)}}{2\times 1.5}
Square -52.5 by squaring both the numerator and the denominator of the fraction.
x=\frac{-\left(-52.5\right)±\sqrt{2756.25-6\left(-4500\right)}}{2\times 1.5}
Multiply -4 times 1.5.
x=\frac{-\left(-52.5\right)±\sqrt{2756.25+27000}}{2\times 1.5}
Multiply -6 times -4500.
x=\frac{-\left(-52.5\right)±\sqrt{29756.25}}{2\times 1.5}
Add 2756.25 to 27000.
x=\frac{-\left(-52.5\right)±\frac{345}{2}}{2\times 1.5}
Take the square root of 29756.25.
x=\frac{52.5±\frac{345}{2}}{2\times 1.5}
The opposite of -52.5 is 52.5.
x=\frac{52.5±\frac{345}{2}}{3}
Multiply 2 times 1.5.
x=\frac{225}{3}
Now solve the equation x=\frac{52.5±\frac{345}{2}}{3} when ± is plus. Add 52.5 to \frac{345}{2} by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.
x=75
Divide 225 by 3.
x=-\frac{120}{3}
Now solve the equation x=\frac{52.5±\frac{345}{2}}{3} when ± is minus. Subtract \frac{345}{2} from 52.5 by finding a common denominator and subtracting the numerators. Then reduce the fraction to lowest terms if possible.
x=-40
Divide -120 by 3.
x=75 x=-40
The equation is now solved.
1.5x^{2}-52.5x-4500=0
Quadratic equations such as this one can be solved by completing the square. In order to complete the square, the equation must first be in the form x^{2}+bx=c.
1.5x^{2}-52.5x-4500-\left(-4500\right)=-\left(-4500\right)
Add 4500 to both sides of the equation.
1.5x^{2}-52.5x=-\left(-4500\right)
Subtracting -4500 from itself leaves 0.
1.5x^{2}-52.5x=4500
Subtract -4500 from 0.
\frac{1.5x^{2}-52.5x}{1.5}=\frac{4500}{1.5}
Divide both sides of the equation by 1.5, which is the same as multiplying both sides by the reciprocal of the fraction.
x^{2}+\left(-\frac{52.5}{1.5}\right)x=\frac{4500}{1.5}
Dividing by 1.5 undoes the multiplication by 1.5.
x^{2}-35x=\frac{4500}{1.5}
Divide -52.5 by 1.5 by multiplying -52.5 by the reciprocal of 1.5.
x^{2}-35x=3000
Divide 4500 by 1.5 by multiplying 4500 by the reciprocal of 1.5.
x^{2}-35x+\left(-\frac{35}{2}\right)^{2}=3000+\left(-\frac{35}{2}\right)^{2}
Divide -35, the coefficient of the x term, by 2 to get -\frac{35}{2}. Then add the square of -\frac{35}{2} to both sides of the equation. This step makes the left hand side of the equation a perfect square.
x^{2}-35x+\frac{1225}{4}=3000+\frac{1225}{4}
Square -\frac{35}{2} by squaring both the numerator and the denominator of the fraction.
x^{2}-35x+\frac{1225}{4}=\frac{13225}{4}
Add 3000 to \frac{1225}{4}.
\left(x-\frac{35}{2}\right)^{2}=\frac{13225}{4}
Factor x^{2}-35x+\frac{1225}{4}. In general, when x^{2}+bx+c is a perfect square, it can always be factored as \left(x+\frac{b}{2}\right)^{2}.
\sqrt{\left(x-\frac{35}{2}\right)^{2}}=\sqrt{\frac{13225}{4}}
Take the square root of both sides of the equation.
x-\frac{35}{2}=\frac{115}{2} x-\frac{35}{2}=-\frac{115}{2}
Simplify.
x=75 x=-40
Add \frac{35}{2} to both sides of the equation.
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