Question

find the equation of the line through (2,3) and rising 4 units for every unit increase in x-axis

Answer 1

slope is 4 ( rising 4 units for every unit increase in x-axis, by definition)
y = ax +b
y = 4x +b,
substitiute x=2, y=3 to find b
3=4*2+b
3=8+b
b=-5
So,
y = 4x -5