a line has a gradient of 3 and passes through the point (-3,3). what is its y intercept?

Question

anonymous · Answer

start with the point - slope formula 
$$y-y_1=m(x-x_1)$$ put $m=3,x_1=-3,y_1=3$ and get 
$$y-3=3(x+3)$$ solve for $y$ to make it look like $y=mx+b$ and your $y$- intercept will be $b$

anonymous · Answer

sorry, i still dont quite get it. so what is the answer? thanks =)

anonymous · Answer

Well, as satellite73 has already outlined the answer, you just have to re-write the equation as:
$$y=3x+12$$. This gives b = 12 which is the y-intercept. To quickly check whether the answer is correct, substitute x = -3 & y=3 in the equation above. It gives an answer 3 = -9 + 12 ==> 3 = 3 
Hope it helps..