Question

Find the equation of the line that passes through the points (-2, 1) and (1, -2).

Answer 1

I'd suggest a 2-step process:
(1) find the slope of the line through these two points. Call it m.
(2) choose one of the given points. Substitute its coordinates and m into the point-slope form of the equation of a straight line.
(3) simplify the result.

Answer 2

find the slope first by using the slope formula
slope(m) = (y2 - y1) / (x2 - x1)
(-2,1) x1 = -2 and y1 = 1
(1,-2) x2 = 1 and y2 = -2
now we sub
slope(m) = (-2 -1) / (1 - (-2)
slope(m) = -3/3 which equals -1
now we will use y = mx + b
slope(m) = -1
(-2,1) x = -2 and y = 1
now sub
1 = -1(-2) + b
1 = 2 + b
1 - 2 = b
-1 = b
so your equation is : y = -x - 1

Answer 3

KM: You could check this result by substituting the x- and y-coordinates of either (or both) points and deciding whether the resulting equation is true or false.

Answer 4

or, like mathmake said, you could have used point slope formula instead of slope intercept formula

Answer 5

oops...mathmale...sorry bout that