how do you find the y-intercept b given a point P?

Question

anonymous · Answer

Hey Joe thanks for taking a look!

anonymous · Answer

what type of equations are we talking about here?  linear equations in the form:
$$y = mx+b$$?

anonymous · Answer

yes

anonymous · Answer

I think it's b = -mx + y but I don't understand why

anonymous · Answer

hmm...yes that is correct, although its a weird way of doing this problem.

This is how they got that:
$$y = mx+b \iff y-mx = mx-mx+b \iff y -mx = b$$

anonymous · Answer

they just subtracted mx from both sides of the equation.

anonymous · Answer

oh! that makes sense! Thanks Joe!

anonymous · Answer

would you use the point slope form

anonymous · Answer

P.Y-Q.Y = M(P.X-Q.X)

anonymous · Answer

where Q.Y and Q.X are Y and X respectively

anonymous · Answer

that way could also work.  if given a slope, and a point on the line, that is the best way.

anonymous · Answer

its just takes a little algebra to get the equation to look like:
$$y = mx+b$$
once you have it looking like that, then getting the y-intercept is as easy as stealing candy from a person that doesnt like candy.  You just write down whatever number b is.