What is the equation of a line which has a gradient of 3 and passes through 4.1?

The general equation of a line is

y = mx + c

If the gradient is 3 then m = 3 so that

y = 3x + c

Since the point (4,1) lies on this line, these coordinates must satisfy the equation.

So 1 = 3*4 + c

ie c = -11

Therefore, the equation is y = 3x - 11