The lines x=4y+a and y=4x+b intersect at the point (1,2). What is a+b
We know that (1,2) is on each line ....so....
1 = 4(2) + a
2 = 4(1) + b
1 = 8 + a
2 = 4 + b
add these
3 = 12 + a +b
3 - 12 = a + b
-9 = a + b
