Question

Use cramers rule to solve 4x+3y=4 -3x-y=7 show your work

Answer 1

`\left\{\begin{array}{ccc}4x+3y=4\\-3x-y=7\end{array}\right\\\\D= \left|\begin{array}{ccc}4&3\\-3&-1\end{array}\right|=(4)(-1)-(-3)(3)=-4+9=5\\\\D_x=\left|\begin{array}{ccc}4&3\\7&-1\end{array}\right|=(4)(-1)-(7)(3)=-4-21=-25\\\\D_y=\left|\begin{array}{ccc}4&4\\-3&7\end{array}\right|=(4)(7)-(-3)(4)=28+12=40\\\\x=(D_x)/(D)\Rightarrow x=(-25)/(5)=-5\\\\y=(D_y)/(D)\Rightarrow y=(40)/(5)=8`