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60\left(1+2x+x^{2}\right)+60\left(1+x\right)+60=198.6
Use binomial theorem \left(a+b\right)^{2}=a^{2}+2ab+b^{2} to expand \left(1+x\right)^{2}.
60+120x+60x^{2}+60\left(1+x\right)+60=198.6
Use the distributive property to multiply 60 by 1+2x+x^{2}.
60+120x+60x^{2}+60+60x+60=198.6
Use the distributive property to multiply 60 by 1+x.
120+120x+60x^{2}+60x+60=198.6
Add 60 and 60 to get 120.
120+180x+60x^{2}+60=198.6
Combine 120x and 60x to get 180x.
180+180x+60x^{2}=198.6
Add 120 and 60 to get 180.
180+180x+60x^{2}-198.6=0
Subtract 198.6 from both sides.
-18.6+180x+60x^{2}=0
Subtract 198.6 from 180 to get -18.6.
60x^{2}+180x-18.6=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{-180±\sqrt{180^{2}-4\times 60\left(-18.6\right)}}{2\times 60}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 60 for a, 180 for b, and -18.6 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
x=\frac{-180±\sqrt{32400-4\times 60\left(-18.6\right)}}{2\times 60}
Square 180.
x=\frac{-180±\sqrt{32400-240\left(-18.6\right)}}{2\times 60}
Multiply -4 times 60.
x=\frac{-180±\sqrt{32400+4464}}{2\times 60}
Multiply -240 times -18.6.
x=\frac{-180±\sqrt{36864}}{2\times 60}
Add 32400 to 4464.
x=\frac{-180±192}{2\times 60}
Take the square root of 36864.
x=\frac{-180±192}{120}
Multiply 2 times 60.
x=\frac{12}{120}
Now solve the equation x=\frac{-180±192}{120} when ± is plus. Add -180 to 192.
x=\frac{1}{10}
Reduce the fraction \frac{12}{120} to lowest terms by extracting and canceling out 12.
x=-\frac{372}{120}
Now solve the equation x=\frac{-180±192}{120} when ± is minus. Subtract 192 from -180.
x=-\frac{31}{10}
Reduce the fraction \frac{-372}{120} to lowest terms by extracting and canceling out 12.
x=\frac{1}{10} x=-\frac{31}{10}
The equation is now solved.
60\left(1+2x+x^{2}\right)+60\left(1+x\right)+60=198.6
Use binomial theorem \left(a+b\right)^{2}=a^{2}+2ab+b^{2} to expand \left(1+x\right)^{2}.
60+120x+60x^{2}+60\left(1+x\right)+60=198.6
Use the distributive property to multiply 60 by 1+2x+x^{2}.
60+120x+60x^{2}+60+60x+60=198.6
Use the distributive property to multiply 60 by 1+x.
120+120x+60x^{2}+60x+60=198.6
Add 60 and 60 to get 120.
120+180x+60x^{2}+60=198.6
Combine 120x and 60x to get 180x.
180+180x+60x^{2}=198.6
Add 120 and 60 to get 180.
180x+60x^{2}=198.6-180
Subtract 180 from both sides.
180x+60x^{2}=18.6
Subtract 180 from 198.6 to get 18.6.
60x^{2}+180x=18.6
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.
\frac{60x^{2}+180x}{60}=\frac{18.6}{60}
Divide both sides by 60.
x^{2}+\frac{180}{60}x=\frac{18.6}{60}
Dividing by 60 undoes the multiplication by 60.
x^{2}+3x=\frac{18.6}{60}
Divide 180 by 60.
x^{2}+3x=0.31
Divide 18.6 by 60.
x^{2}+3x+\left(\frac{3}{2}\right)^{2}=0.31+\left(\frac{3}{2}\right)^{2}
Divide 3, the coefficient of the x term, by 2 to get \frac{3}{2}. Then add the square of \frac{3}{2} to both sides of the equation. This step makes the left hand side of the equation a perfect square.
x^{2}+3x+\frac{9}{4}=0.31+\frac{9}{4}
Square \frac{3}{2} by squaring both the numerator and the denominator of the fraction.
x^{2}+3x+\frac{9}{4}=\frac{64}{25}
Add 0.31 to \frac{9}{4} by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.
\left(x+\frac{3}{2}\right)^{2}=\frac{64}{25}
Factor x^{2}+3x+\frac{9}{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{3}{2}\right)^{2}}=\sqrt{\frac{64}{25}}
Take the square root of both sides of the equation.
x+\frac{3}{2}=\frac{8}{5} x+\frac{3}{2}=-\frac{8}{5}
Simplify.
x=\frac{1}{10} x=-\frac{31}{10}
Subtract \frac{3}{2} from both sides of the equation.