The points (1, 3) and (−3, 7) lie on a line. where does the line cross the x-axis?

First, we find the equation of the line...

(1,3),(-3,7)
slope = (7 - 3) / (-3 - 1) = 4/-4 = -1

y = mx + b
slope(m) = -1
use either of ur points (1,3)...x = 1 and y = 3
now sub into the formula and find b, the y int
3 = -1(1) + b
3 = -1 + b
3 + 1 = b
4 = b
so the equation for this line is : y = -1x + 4 which is usually written as :
 y = -x + 4

Now...to find where the line crosses the x axis (or the x intercept)...we sub in 0 for y and solve for x

y = -x + 4
0 = -x + 4
x = 4... so ur x intercept (where the line crosses the x axis) is : (4,0)