Solve {l}{frac{2sqrt{5}}{5}x+frac{sqrt{5}}{5}y=3/5}{frac{sqrt{5}}{5}x-frac{2sqrt{5}}{5}y=-4/5}

$$\left\{ \begin{array} { l } { \frac { 2 \sqrt { 5 } } { 5 } x + \frac { \sqrt { 5 } } { 5 } y = \frac { 3 } { 5 } } \\ { \frac { \sqrt { 5 } } { 5 } x - \frac { 2 \sqrt { 5 } } { 5 } y = - \frac { 4 } { 5 } } \end{array} \right.$$

Solve for x, y

$$x=\frac{2\sqrt{5}}{25}\approx 0.178885438$$

$$y=\frac{11\sqrt{5}}{25}\approx 0.98386991$$

Steps Using Substitution

Consider the first equation. Multiply both sides of the equation by 5.

$$2\sqrt{5}x+\sqrt{5}y=3$$

Consider the second equation. Multiply both sides of the equation by 5.

$$\sqrt{5}x-2\sqrt{5}y=-4$$

To solve a pair of equations using substitution, first solve one of the equations for one of the variables. Then substitute the result for that variable in the other equation.

$$2\sqrt{5}x+\sqrt{5}y=3,\sqrt{5}x+\left(-2\sqrt{5}\right)y=-4$$

Choose one of the equations and solve it for x by isolating x on the left hand side of the equal sign.

$$2\sqrt{5}x+\sqrt{5}y=3$$

Subtract \sqrt{5}y from both sides of the equation.

$$2\sqrt{5}x=\left(-\sqrt{5}\right)y+3$$

Divide both sides by 2\sqrt{5}.

$$x=\frac{\sqrt{5}}{10}\left(\left(-\sqrt{5}\right)y+3\right)$$

Multiply \frac{\sqrt{5}}{10} times -\sqrt{5}y+3.

$$x=-\frac{1}{2}y+\frac{3\sqrt{5}}{10}$$

Substitute -\frac{y}{2}+\frac{3\sqrt{5}}{10} for x in the other equation, \sqrt{5}x+\left(-2\sqrt{5}\right)y=-4.

$$\sqrt{5}\left(-\frac{1}{2}y+\frac{3\sqrt{5}}{10}\right)+\left(-2\sqrt{5}\right)y=-4$$

Multiply \sqrt{5} times -\frac{y}{2}+\frac{3\sqrt{5}}{10}.

$$\left(-\frac{\sqrt{5}}{2}\right)y+\frac{3}{2}+\left(-2\sqrt{5}\right)y=-4$$

Add -\frac{\sqrt{5}y}{2} to -2\sqrt{5}y.

$$\left(-\frac{5\sqrt{5}}{2}\right)y+\frac{3}{2}=-4$$

Subtract \frac{3}{2} from both sides of the equation.

$$\left(-\frac{5\sqrt{5}}{2}\right)y=-\frac{11}{2}$$

Divide both sides by -\frac{5\sqrt{5}}{2}.

$$y=\frac{11\sqrt{5}}{25}$$

Substitute \frac{11\sqrt{5}}{25} for y in x=-\frac{1}{2}y+\frac{3\sqrt{5}}{10}. Because the resulting equation contains only one variable, you can solve for x directly.

$$x=-\frac{1}{2}\times \frac{11\sqrt{5}}{25}+\frac{3\sqrt{5}}{10}$$

Multiply -\frac{1}{2} times \frac{11\sqrt{5}}{25}.

$$x=-\frac{11\sqrt{5}}{50}+\frac{3\sqrt{5}}{10}$$

Add \frac{3\sqrt{5}}{10} to -\frac{11\sqrt{5}}{50}.

$$x=\frac{2\sqrt{5}}{25}$$

The system is now solved.

$$x=\frac{2\sqrt{5}}{25},y=\frac{11\sqrt{5}}{25}$$

Steps Using Elimination

Consider the first equation. Multiply both sides of the equation by 5.

$$2\sqrt{5}x+\sqrt{5}y=3$$

Consider the second equation. Multiply both sides of the equation by 5.

$$\sqrt{5}x-2\sqrt{5}y=-4$$

In order to solve by elimination, coefficients of one of the variables must be the same in both equations so that the variable will cancel out when one equation is subtracted from the other.

$$2\sqrt{5}x+\sqrt{5}y=3,\sqrt{5}x+\left(-2\sqrt{5}\right)y=-4$$

To make 2\sqrt{5}x and \sqrt{5}x equal, multiply all terms on each side of the first equation by \sqrt{5} and all terms on each side of the second by 2\sqrt{5}.

$$\sqrt{5}\times 2\sqrt{5}x+\sqrt{5}\sqrt{5}y=\sqrt{5}\times 3,2\sqrt{5}\sqrt{5}x+2\sqrt{5}\left(-2\sqrt{5}\right)y=2\sqrt{5}\left(-4\right)$$

Simplify.

$$10x+5y=3\sqrt{5},10x-20y=-8\sqrt{5}$$

Subtract 10x-20y=-8\sqrt{5} from 10x+5y=3\sqrt{5} by subtracting like terms on each side of the equal sign.

$$10x-10x+5y+20y=3\sqrt{5}+8\sqrt{5}$$

Add 10x to -10x. Terms 10x and -10x cancel out, leaving an equation with only one variable that can be solved.

$$5y+20y=3\sqrt{5}+8\sqrt{5}$$

Add 5y to 20y.

$$25y=3\sqrt{5}+8\sqrt{5}$$

Add 3\sqrt{5} to 8\sqrt{5}.

$$25y=11\sqrt{5}$$

Divide both sides by 25.

$$y=\frac{11\sqrt{5}}{25}$$

Substitute \frac{11\sqrt{5}}{25} for y in \sqrt{5}x+\left(-2\sqrt{5}\right)y=-4. Because the resulting equation contains only one variable, you can solve for x directly.

$$\sqrt{5}x+\left(-2\sqrt{5}\right)\times \frac{11\sqrt{5}}{25}=-4$$

Multiply -2\sqrt{5} times \frac{11\sqrt{5}}{25}.

$$\sqrt{5}x-\frac{22}{5}=-4$$

Add \frac{22}{5} to both sides of the equation.

$$\sqrt{5}x=\frac{2}{5}$$

Divide both sides by \sqrt{5}.

$$x=\frac{2\sqrt{5}}{25}$$

The system is now solved.

$$x=\frac{2\sqrt{5}}{25},y=\frac{11\sqrt{5}}{25}$$