Question

Find "a" if coficient of line which passes through points
P1 (-3,1) and P2(a,a) is 1/a

Answer 1

anyone ?

Answer 2

you're supposed to know this formula:
\[\LARGE (y-y_1)=\frac{y_2-y_1}{x_2-x_1} (x-x_1)\]

now \[\LARGE k=\frac{y_2-y_1}{x_2-x_1}\]

k=1/a substitute... and there you go !