If we are talking a² + b² = c² instead of looking for the hypotenuse we look for a leg and it doesnt matter where it is placed.. so for there forth you'll do
24² + b² = 40²
and then from there you square all the numbers so then you get
576 + b² = 1600
then subtract 576 from both sides so you are left with
because the equation y=9x does not have a y-intercept (all slopes come in the form y=mx+b -- it can be written differently though) and since there is no 'b' that means the y-intercept is 0. So whenever there is no y-intercept, the slope starts at 0.