Solve 3x^2-50x-1500=3800

$$3 { x }^{ 2 } -50x-1500 = 3800$$

Solve for x

$$x = \frac{5 \sqrt{661} + 25}{3} \approx 51.183200441$$

$$x=\frac{25-5\sqrt{661}}{3}\approx -34.516533774$$

Steps Using the Quadratic Formula

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.

$$3x^{2}-50x-1500=3800$$

Subtract 3800 from both sides of the equation.

$$3x^{2}-50x-1500-3800=3800-3800$$

Subtracting 3800 from itself leaves 0.

$$3x^{2}-50x-1500-3800=0$$

Subtract 3800 from -1500.

$$3x^{2}-50x-5300=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 3 for a, -50 for b, and -5300 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{-\left(-50\right)±\sqrt{\left(-50\right)^{2}-4\times 3\left(-5300\right)}}{2\times 3}$$

Square -50.

$$x=\frac{-\left(-50\right)±\sqrt{2500-4\times 3\left(-5300\right)}}{2\times 3}$$

Multiply -4 times 3.

$$x=\frac{-\left(-50\right)±\sqrt{2500-12\left(-5300\right)}}{2\times 3}$$

Multiply -12 times -5300.

$$x=\frac{-\left(-50\right)±\sqrt{2500+63600}}{2\times 3}$$

Add 2500 to 63600.

$$x=\frac{-\left(-50\right)±\sqrt{66100}}{2\times 3}$$

Take the square root of 66100.

$$x=\frac{-\left(-50\right)±10\sqrt{661}}{2\times 3}$$

The opposite of -50 is 50.

$$x=\frac{50±10\sqrt{661}}{2\times 3}$$

Multiply 2 times 3.

$$x=\frac{50±10\sqrt{661}}{6}$$

Now solve the equation x=\frac{50±10\sqrt{661}}{6} when ± is plus. Add 50 to 10\sqrt{661}.

$$x=\frac{10\sqrt{661}+50}{6}$$

Divide 50+10\sqrt{661} by 6.

$$x=\frac{5\sqrt{661}+25}{3}$$

Now solve the equation x=\frac{50±10\sqrt{661}}{6} when ± is minus. Subtract 10\sqrt{661} from 50.

$$x=\frac{50-10\sqrt{661}}{6}$$

Divide 50-10\sqrt{661} by 6.

$$x=\frac{25-5\sqrt{661}}{3}$$

The equation is now solved.

$$x=\frac{5\sqrt{661}+25}{3} x=\frac{25-5\sqrt{661}}{3}$$

Steps for Completing the Square

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.

$$3x^{2}-50x-1500=3800$$

Add 1500 to both sides of the equation.

$$3x^{2}-50x-1500-\left(-1500\right)=3800-\left(-1500\right)$$

Subtracting -1500 from itself leaves 0.

$$3x^{2}-50x=3800-\left(-1500\right)$$

Subtract -1500 from 3800.

$$3x^{2}-50x=5300$$

Divide both sides by 3.

$$\frac{3x^{2}-50x}{3}=\frac{5300}{3}$$

Dividing by 3 undoes the multiplication by 3.

$$x^{2}-\frac{50}{3}x=\frac{5300}{3}$$

Divide -\frac{50}{3}, the coefficient of the x term, by 2 to get -\frac{25}{3}. Then add the square of -\frac{25}{3} to both sides of the equation. This step makes the left hand side of the equation a perfect square.

$$x^{2}-\frac{50}{3}x+\left(-\frac{25}{3}\right)^{2}=\frac{5300}{3}+\left(-\frac{25}{3}\right)^{2}$$

Square -\frac{25}{3} by squaring both the numerator and the denominator of the fraction.

$$x^{2}-\frac{50}{3}x+\frac{625}{9}=\frac{5300}{3}+\frac{625}{9}$$

Add \frac{5300}{3} to \frac{625}{9} by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.

$$x^{2}-\frac{50}{3}x+\frac{625}{9}=\frac{16525}{9}$$

Factor x^{2}-\frac{50}{3}x+\frac{625}{9}. In general, when x^{2}+bx+c is a perfect square, it can always be factored as \left(x+\frac{b}{2}\right)^{2}.

$$\left(x-\frac{25}{3}\right)^{2}=\frac{16525}{9}$$

Take the square root of both sides of the equation.

$$\sqrt{\left(x-\frac{25}{3}\right)^{2}}=\sqrt{\frac{16525}{9}}$$

Simplify.

$$x-\frac{25}{3}=\frac{5\sqrt{661}}{3} x-\frac{25}{3}=-\frac{5\sqrt{661}}{3}$$

Add \frac{25}{3} to both sides of the equation.

$$x=\frac{5\sqrt{661}+25}{3} x=\frac{25-5\sqrt{661}}{3}$$