Question

A line passes through the points (-8, 1) and (-1, 6). A second line passes through the points (-3,0) and (-8,-5). What is the point of intersection of the two lines?

Answer 1

$\begin{gathered} y=mx+b \\ m=\frac{6-1}{-1+8}=\frac{5}{7} \\ 6=\frac{5}{7}(-1)+b \\ 6+\frac{5}{7}=b \\ b=\frac{42+5}{7}=\frac{47}{7} \\ y=\frac{5}{7}x+\frac{47}{7} \end{gathered}$

For the second line

$\begin{gathered} y=mx+b \\ m=\frac{-5-0}{-8+3}=\frac{-5}{-5}=1 \\ 0=1(-3)+b \\ b=3 \\ y=x+3 \end{gathered}$

The intersection will be

$\begin{gathered} y=\frac{5}{7}x+\frac{47}{7} \\ x+3=\frac{5}{7}x+\frac{47}{7} \\ x-\frac{5}{7}x=\frac{47}{7}-3 \\ \frac{7x-5x}{7}=\frac{47-21}{7} \\ \frac{2x}{7}=\frac{26}{7} \\ 14x=182 \\ x=\frac{182}{14} \\ x=13 \\ \\ y=13+3=16 \end{gathered}$

Therefore, the point of intersection is (13, 16)