Solve {l}{815679x-4y=-9697}{1688135y+30x=-601347}

$$\left. \begin{array} { l } { 815679 x - 4 y = - 9697 } \\ { 1688135 y + 30 x = - 601347 } \end{array} \right.$$

Solve for x, y

$$x=-\frac{16372250483}{1376976268785}\approx -0.011890002$$

$$y=-\frac{163501942901}{458992089595}\approx -0.356219522$$

Steps Using Substitution

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.

$$815679x-4y=-9697,30x+1688135y=-601347$$

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

$$815679x-4y=-9697$$

Add 4y to both sides of the equation.

$$815679x=4y-9697$$

Divide both sides by 815679.

$$x=\frac{1}{815679}\left(4y-9697\right)$$

Multiply \frac{1}{815679} times 4y-9697.

$$x=\frac{4}{815679}y-\frac{9697}{815679}$$

Substitute \frac{4y-9697}{815679} for x in the other equation, 30x+1688135y=-601347.

$$30\left(\frac{4}{815679}y-\frac{9697}{815679}\right)+1688135y=-601347$$

Multiply 30 times \frac{4y-9697}{815679}.

$$\frac{40}{271893}y-\frac{96970}{271893}+1688135y=-601347$$

Add \frac{40y}{271893} to 1688135y.

$$\frac{458992089595}{271893}y-\frac{96970}{271893}=-601347$$

Add \frac{96970}{271893} to both sides of the equation.

$$\frac{458992089595}{271893}y=-\frac{163501942901}{271893}$$

Divide both sides of the equation by \frac{458992089595}{271893}, which is the same as multiplying both sides by the reciprocal of the fraction.

$$y=-\frac{163501942901}{458992089595}$$

Substitute -\frac{163501942901}{458992089595} for y in x=\frac{4}{815679}y-\frac{9697}{815679}. Because the resulting equation contains only one variable, you can solve for x directly.

$$x=\frac{4}{815679}\left(-\frac{163501942901}{458992089595}\right)-\frac{9697}{815679}$$

Multiply \frac{4}{815679} times -\frac{163501942901}{458992089595} by multiplying numerator times numerator and denominator times denominator. Then reduce the fraction to lowest terms if possible.

$$x=-\frac{654007771604}{374390208648760005}-\frac{9697}{815679}$$

Add -\frac{9697}{815679} to -\frac{654007771604}{374390208648760005} by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.

$$x=-\frac{16372250483}{1376976268785}$$

The system is now solved.

$$x=-\frac{16372250483}{1376976268785},y=-\frac{163501942901}{458992089595}$$

Steps Using Matrices

Put the equations in standard form and then use matrices to solve the system of equations.

$$815679x-4y=-9697,30x+1688135y=-601347$$

Write the equations in matrix form.

$$\left(\begin{matrix}815679&-4\\30&1688135\end{matrix}\right)\left(\begin{matrix}x\\y\end{matrix}\right)=\left(\begin{matrix}-9697\\-601347\end{matrix}\right)$$

Left multiply the equation by the inverse matrix of \left(\begin{matrix}815679&-4\\30&1688135\end{matrix}\right).

$$inverse(\left(\begin{matrix}815679&-4\\30&1688135\end{matrix}\right))\left(\begin{matrix}815679&-4\\30&1688135\end{matrix}\right)\left(\begin{matrix}x\\y\end{matrix}\right)=inverse(\left(\begin{matrix}815679&-4\\30&1688135\end{matrix}\right))\left(\begin{matrix}-9697\\-601347\end{matrix}\right)$$

The product of a matrix and its inverse is the identity matrix.

$$\left(\begin{matrix}1&0\\0&1\end{matrix}\right)\left(\begin{matrix}x\\y\end{matrix}\right)=inverse(\left(\begin{matrix}815679&-4\\30&1688135\end{matrix}\right))\left(\begin{matrix}-9697\\-601347\end{matrix}\right)$$

Multiply the matrices on the left hand side of the equal sign.

$$\left(\begin{matrix}x\\y\end{matrix}\right)=inverse(\left(\begin{matrix}815679&-4\\30&1688135\end{matrix}\right))\left(\begin{matrix}-9697\\-601347\end{matrix}\right)$$

For the 2\times 2 matrix \left(\begin{matrix}a&b\\c&d\end{matrix}\right), the inverse matrix is \left(\begin{matrix}\frac{d}{ad-bc}&\frac{-b}{ad-bc}\\\frac{-c}{ad-bc}&\frac{a}{ad-bc}\end{matrix}\right), so the matrix equation can be rewritten as a matrix multiplication problem.

$$\left(\begin{matrix}x\\y\end{matrix}\right)=\left(\begin{matrix}\frac{1688135}{815679\times 1688135-\left(-4\times 30\right)}&-\frac{-4}{815679\times 1688135-\left(-4\times 30\right)}\\-\frac{30}{815679\times 1688135-\left(-4\times 30\right)}&\frac{815679}{815679\times 1688135-\left(-4\times 30\right)}\end{matrix}\right)\left(\begin{matrix}-9697\\-601347\end{matrix}\right)$$

Do the arithmetic.

$$\left(\begin{matrix}x\\y\end{matrix}\right)=\left(\begin{matrix}\frac{337627}{275395253757}&\frac{4}{1376976268785}\\-\frac{2}{91798417919}&\frac{271893}{458992089595}\end{matrix}\right)\left(\begin{matrix}-9697\\-601347\end{matrix}\right)$$

Multiply the matrices.

$$\left(\begin{matrix}x\\y\end{matrix}\right)=\left(\begin{matrix}\frac{337627}{275395253757}\left(-9697\right)+\frac{4}{1376976268785}\left(-601347\right)\\-\frac{2}{91798417919}\left(-9697\right)+\frac{271893}{458992089595}\left(-601347\right)\end{matrix}\right)$$

Do the arithmetic.

$$\left(\begin{matrix}x\\y\end{matrix}\right)=\left(\begin{matrix}-\frac{16372250483}{1376976268785}\\-\frac{163501942901}{458992089595}\end{matrix}\right)$$

Extract the matrix elements x and y.

$$x=-\frac{16372250483}{1376976268785},y=-\frac{163501942901}{458992089595}$$

Steps Using Elimination

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.

$$815679x-4y=-9697,30x+1688135y=-601347$$

To make 815679x and 30x equal, multiply all terms on each side of the first equation by 30 and all terms on each side of the second by 815679.

$$30\times 815679x+30\left(-4\right)y=30\left(-9697\right),815679\times 30x+815679\times 1688135y=815679\left(-601347\right)$$

Simplify.

$$24470370x-120y=-290910,24470370x+1376976268665y=-490506119613$$

Subtract 24470370x+1376976268665y=-490506119613 from 24470370x-120y=-290910 by subtracting like terms on each side of the equal sign.

$$24470370x-24470370x-120y-1376976268665y=-290910+490506119613$$

Add 24470370x to -24470370x. Terms 24470370x and -24470370x cancel out, leaving an equation with only one variable that can be solved.

$$-120y-1376976268665y=-290910+490506119613$$

Add -120y to -1376976268665y.

$$-1376976268785y=-290910+490506119613$$

Add -290910 to 490506119613.

$$-1376976268785y=490505828703$$

Divide both sides by -1376976268785.

$$y=-\frac{163501942901}{458992089595}$$

Substitute -\frac{163501942901}{458992089595} for y in 30x+1688135y=-601347. Because the resulting equation contains only one variable, you can solve for x directly.

$$30x+1688135\left(-\frac{163501942901}{458992089595}\right)=-601347$$

Multiply 1688135 times -\frac{163501942901}{458992089595}.

$$30x-\frac{55202670475835927}{91798417919}=-601347$$

Add \frac{55202670475835927}{91798417919} to both sides of the equation.

$$30x=-\frac{32744500966}{91798417919}$$

Divide both sides by 30.

$$x=-\frac{16372250483}{1376976268785}$$

The system is now solved.

$$x=-\frac{16372250483}{1376976268785},y=-\frac{163501942901}{458992089595}$$