Solve 10x^2-6.5x+0.75=0

$$10 x ^ { 2 } - 6.5 x + 0.75 = 0$$

Solve for x

$$x=0.15$$

$$x=0.5$$

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.

$$10x^{2}-6.5x+0.75=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 10 for a, -6.5 for b, and 0.75 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{-\left(-6.5\right)±\sqrt{\left(-6.5\right)^{2}-4\times 10\times 0.75}}{2\times 10}$$

Square -6.5 by squaring both the numerator and the denominator of the fraction.

$$x=\frac{-\left(-6.5\right)±\sqrt{42.25-4\times 10\times 0.75}}{2\times 10}$$

Multiply -4 times 10.

$$x=\frac{-\left(-6.5\right)±\sqrt{42.25-40\times 0.75}}{2\times 10}$$

Multiply -40 times 0.75.

$$x=\frac{-\left(-6.5\right)±\sqrt{42.25-30}}{2\times 10}$$

Add 42.25 to -30.

$$x=\frac{-\left(-6.5\right)±\sqrt{12.25}}{2\times 10}$$

Take the square root of 12.25.

$$x=\frac{-\left(-6.5\right)±\frac{7}{2}}{2\times 10}$$

The opposite of -6.5 is 6.5.

$$x=\frac{6.5±\frac{7}{2}}{2\times 10}$$

Multiply 2 times 10.

$$x=\frac{6.5±\frac{7}{2}}{20}$$

Now solve the equation x=\frac{6.5±\frac{7}{2}}{20} when ± is plus. Add 6.5 to \frac{7}{2} by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.

$$x=\frac{10}{20}$$

Reduce the fraction \frac{10}{20} to lowest terms by extracting and canceling out 10.

$$x=\frac{1}{2}$$

Now solve the equation x=\frac{6.5±\frac{7}{2}}{20} when ± is minus. Subtract \frac{7}{2} from 6.5 by finding a common denominator and subtracting the numerators. Then reduce the fraction to lowest terms if possible.

$$x=\frac{3}{20}$$

The equation is now solved.

$$x=\frac{1}{2} x=\frac{3}{20}$$

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.

$$10x^{2}-6.5x+0.75=0$$

Subtract 0.75 from both sides of the equation.

$$10x^{2}-6.5x+0.75-0.75=-0.75$$

Subtracting 0.75 from itself leaves 0.

$$10x^{2}-6.5x=-0.75$$

Divide both sides by 10.

$$\frac{10x^{2}-6.5x}{10}=-\frac{0.75}{10}$$

Dividing by 10 undoes the multiplication by 10.

$$x^{2}+\left(-\frac{6.5}{10}\right)x=-\frac{0.75}{10}$$

Divide -6.5 by 10.

$$x^{2}-0.65x=-\frac{0.75}{10}$$

Divide -0.75 by 10.

$$x^{2}-0.65x=-0.075$$

Divide -0.65, the coefficient of the x term, by 2 to get -0.325. Then add the square of -0.325 to both sides of the equation. This step makes the left hand side of the equation a perfect square.

$$x^{2}-0.65x+\left(-0.325\right)^{2}=-0.075+\left(-0.325\right)^{2}$$

Square -0.325 by squaring both the numerator and the denominator of the fraction.

$$x^{2}-0.65x+0.105625=-0.075+0.105625$$

Add -0.075 to 0.105625 by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.

$$x^{2}-0.65x+0.105625=0.030625$$

Factor x^{2}-0.65x+0.105625. In general, when x^{2}+bx+c is a perfect square, it can always be factored as \left(x+\frac{b}{2}\right)^{2}.

$$\left(x-0.325\right)^{2}=0.030625$$

Take the square root of both sides of the equation.

$$\sqrt{\left(x-0.325\right)^{2}}=\sqrt{0.030625}$$

Simplify.

$$x-0.325=\frac{7}{40} x-0.325=-\frac{7}{40}$$

Add 0.325 to both sides of the equation.

$$x=\frac{1}{2} x=\frac{3}{20}$$