Step-by-step explanation:
a. Substituting (0,b) into the point-slope form, we get y = mx + b. Plug in 0 to the x1 value and plug in b into the y1 value. Add b to both sides and you should get y = mx+b.
b. Slope-intercept shows how to get specific x or y values at a point if three of the four variables (y, m, x, or b) are known. Point slope form is used mainly when finding the slope from two distinct points. (Later, you'll learn it's importance in the definition of a derivative :).)
c. y = mx + b. Refer to a.
