Solve {l}{a/4-bln1/2+1/2=1+ln2}{a-2b=0}

$$\left\{ \begin{array} { l } { \frac { a } { 4 } - b \ln \frac { 1 } { 2 } + \frac { 1 } { 2 } = 1 + \ln 2 } \\ { a - 2 b = 0 } \end{array} \right.$$

Solve for a, b

$$a=2$$

$$b=1$$

Steps Using Substitution

Consider the first equation. Multiply both sides of the equation by 4, the least common multiple of 4,2.

$$4\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)+2=4+4\ln(2)$$

Subtract 2 from both sides.

$$4\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=4+4\ln(2)-2$$

Subtract 2 from 4 to get 2.

$$4\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=2+4\ln(2)$$

Multiply both sides of the equation by 4.

$$16\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=8+16\ln(2)$$

Multiply both sides of the equation by 4.

$$64\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=32+64\ln(2)$$

Use the distributive property to multiply 64 by \frac{a}{4}-b\ln(\frac{1}{2}).

$$64\times \frac{a}{4}+64\ln(2)b=32+64\ln(2)$$

Cancel out 4, the greatest common factor in 64 and 4.

$$16a+64\ln(2)b=32+64\ln(2)$$

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.

$$16a+64\ln(2)b=64\ln(2)+32,a-2b=0$$

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

$$16a+64\ln(2)b=64\ln(2)+32$$

Subtract 64\ln(2)b from both sides of the equation.

$$16a=\left(-64\ln(2)\right)b+64\ln(2)+32$$

Divide both sides by 16.

$$a=\frac{1}{16}\left(\left(-64\ln(2)\right)b+64\ln(2)+32\right)$$

Multiply \frac{1}{16} times -64\ln(2)b+32+64\ln(2).

$$a=\left(-4\ln(2)\right)b+4\ln(2)+2$$

Substitute -4\ln(2)b+2+4\ln(2) for a in the other equation, a-2b=0.

$$\left(-4\ln(2)\right)b+4\ln(2)+2-2b=0$$

Add -4\ln(2)b to -2b.

$$\left(-4\ln(2)-2\right)b+4\ln(2)+2=0$$

Subtract 2+4\ln(2) from both sides of the equation.

$$\left(-4\ln(2)-2\right)b=-4\ln(2)-2$$

Divide both sides by -4\ln(2)-2.

$$b=1$$

Substitute 1 for b in a=\left(-4\ln(2)\right)b+4\ln(2)+2. Because the resulting equation contains only one variable, you can solve for a directly.

$$a=-4\ln(2)+4\ln(2)+2$$

Add 2+4\ln(2) to -4\ln(2).

$$a=2$$

The system is now solved.

$$a=2,b=1$$

Steps Using Matrices

Consider the first equation. Multiply both sides of the equation by 4, the least common multiple of 4,2.

$$4\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)+2=4+4\ln(2)$$

Subtract 2 from both sides.

$$4\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=4+4\ln(2)-2$$

Subtract 2 from 4 to get 2.

$$4\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=2+4\ln(2)$$

Multiply both sides of the equation by 4.

$$16\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=8+16\ln(2)$$

Multiply both sides of the equation by 4.

$$64\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=32+64\ln(2)$$

Use the distributive property to multiply 64 by \frac{a}{4}-b\ln(\frac{1}{2}).

$$64\times \frac{a}{4}+64\ln(2)b=32+64\ln(2)$$

Cancel out 4, the greatest common factor in 64 and 4.

$$16a+64\ln(2)b=32+64\ln(2)$$

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

$$16a+64\ln(2)b=64\ln(2)+32,a-2b=0$$

Write the equations in matrix form.

$$\left(\begin{matrix}16&64\ln(2)\\1&-2\end{matrix}\right)\left(\begin{matrix}a\\b\end{matrix}\right)=\left(\begin{matrix}64\ln(2)+32\\0\end{matrix}\right)$$

Left multiply the equation by the inverse matrix of \left(\begin{matrix}16&64\ln(2)\\1&-2\end{matrix}\right).

$$inverse(\left(\begin{matrix}16&64\ln(2)\\1&-2\end{matrix}\right))\left(\begin{matrix}16&64\ln(2)\\1&-2\end{matrix}\right)\left(\begin{matrix}a\\b\end{matrix}\right)=inverse(\left(\begin{matrix}16&64\ln(2)\\1&-2\end{matrix}\right))\left(\begin{matrix}64\ln(2)+32\\0\end{matrix}\right)$$

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

$$\left(\begin{matrix}1&0\\0&1\end{matrix}\right)\left(\begin{matrix}a\\b\end{matrix}\right)=inverse(\left(\begin{matrix}16&64\ln(2)\\1&-2\end{matrix}\right))\left(\begin{matrix}64\ln(2)+32\\0\end{matrix}\right)$$

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

$$\left(\begin{matrix}a\\b\end{matrix}\right)=inverse(\left(\begin{matrix}16&64\ln(2)\\1&-2\end{matrix}\right))\left(\begin{matrix}64\ln(2)+32\\0\end{matrix}\right)$$

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.

$$\left(\begin{matrix}a\\b\end{matrix}\right)=\left(\begin{matrix}-\frac{2}{16\left(-2\right)-64\ln(2)}&-\frac{64\ln(2)}{16\left(-2\right)-64\ln(2)}\\-\frac{1}{16\left(-2\right)-64\ln(2)}&\frac{16}{16\left(-2\right)-64\ln(2)}\end{matrix}\right)\left(\begin{matrix}64\ln(2)+32\\0\end{matrix}\right)$$

Do the arithmetic.

$$\left(\begin{matrix}a\\b\end{matrix}\right)=\left(\begin{matrix}\frac{1}{16\left(2\ln(2)+1\right)}&\frac{2\ln(2)}{2\ln(2)+1}\\\frac{1}{32\left(2\ln(2)+1\right)}&-\frac{1}{2\left(2\ln(2)+1\right)}\end{matrix}\right)\left(\begin{matrix}64\ln(2)+32\\0\end{matrix}\right)$$

Multiply the matrices.

$$\left(\begin{matrix}a\\b\end{matrix}\right)=\left(\begin{matrix}\frac{1}{16\left(2\ln(2)+1\right)}\left(64\ln(2)+32\right)\\\frac{1}{32\left(2\ln(2)+1\right)}\left(64\ln(2)+32\right)\end{matrix}\right)$$

Do the arithmetic.

$$\left(\begin{matrix}a\\b\end{matrix}\right)=\left(\begin{matrix}2\\1\end{matrix}\right)$$

Extract the matrix elements a and b.

$$a=2,b=1$$

Steps Using Elimination

Consider the first equation. Multiply both sides of the equation by 4, the least common multiple of 4,2.

$$4\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)+2=4+4\ln(2)$$

Subtract 2 from both sides.

$$4\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=4+4\ln(2)-2$$

Subtract 2 from 4 to get 2.

$$4\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=2+4\ln(2)$$

Multiply both sides of the equation by 4.

$$16\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=8+16\ln(2)$$

Multiply both sides of the equation by 4.

$$64\left(\frac{a}{4}-b\ln(\frac{1}{2})\right)=32+64\ln(2)$$

Use the distributive property to multiply 64 by \frac{a}{4}-b\ln(\frac{1}{2}).

$$64\times \frac{a}{4}+64\ln(2)b=32+64\ln(2)$$

Cancel out 4, the greatest common factor in 64 and 4.

$$16a+64\ln(2)b=32+64\ln(2)$$

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.

$$16a+64\ln(2)b=64\ln(2)+32,a-2b=0$$

To make 16a and a equal, multiply all terms on each side of the first equation by 1 and all terms on each side of the second by 16.

$$16a+64\ln(2)b=64\ln(2)+32,16a+16\left(-2\right)b=0$$

Simplify.

$$16a+64\ln(2)b=64\ln(2)+32,16a-32b=0$$

Subtract 16a-32b=0 from 16a+64\ln(2)b=64\ln(2)+32 by subtracting like terms on each side of the equal sign.

$$16a-16a+64\ln(2)b+32b=64\ln(2)+32$$

Add 16a to -16a. Terms 16a and -16a cancel out, leaving an equation with only one variable that can be solved.

$$64\ln(2)b+32b=64\ln(2)+32$$

Add 64\ln(2)b to 32b.

$$\left(64\ln(2)+32\right)b=64\ln(2)+32$$

Divide both sides by 32+64\ln(2).

$$b=1$$

Substitute 1 for b in a-2b=0. Because the resulting equation contains only one variable, you can solve for a directly.

$$a-2=0$$

Add 2 to both sides of the equation.

$$a=2$$

The system is now solved.

$$a=2,b=1$$