hi. how do i write an equation for a line?

Question

i need this please...i'll give points right away for a detailed answer

Answer 1

It depends on what information you know ahead of time.

If you know the slope and the y-intercept (where the line crosses the y-axis), you'd use slope/intercept form, with the general rule of y = mx + b (where m = slope and b = y-intercept), so if they told you the slope was 3/4 and the y-intercept was -7, the equation would be y = .75x - 7 .

If you know the point and a slope (a very common algebra book problem), you'd use the point/slope formula y - y1 = m(x - x1). Here (x1,y1) is the point you were given, and m is the slope. So if you were given the point (-4,5) and a slope of 3, the equation would be y - 5 = 3(x + 4) Note the signs in the equation are the opposite of what they were in the point.

Sometimes you're given two points. The first thing you do is find the slope with the formula m = (y2 - y1)/(x2 - x1). Then you can take EITHER of the points and plug into the point/slope formula.

Double-check to see if your book or teacher wants the answer in a specific form. You may need to do some algebra to get the answer you have into the form they want.