Write the equation of a line through the points (−7,14) and (−21,28) in slope-intercept form

y= -x + 7

Solution:

Step 1 : find the slope using the equation using the pair of coordinates that are given i.e A (−7,14)  B (−21,28) ( name them A and B respectively so they can be easily named as x1, y1 and x2,y2 respectively)

m = y2-y1/x2-x1

m = 28-14 / -21 -( -7)

m =  14 / -14

m = -1

Step 2 : Find the y intercept using the line of equation (use and one of the given coordinates either A or B)

Using A ( -7, 14)

y= mx+ b

14 = (-1)(-7) + b

14= 7 + b

14-7 = b

7 =b

So,

y=mx+b

Insert m and b

y= -x + 7

she will travel a distance in the range of 3 - 11 miles