Question

Bookwork code: E13 Work out the equation of the straight line shown below. Give your answer in the form y = mx + c, where m and care integers or fractions in their simplest forms. 7 4- 3. 2- 1- -6 -5 -4 -3 -2 -1.0 -1- --2- --3- -4- -5- Calculator not allowed T 2 3 4 5 6 X​

Answer 1

y = -5x +4

Explanation:

You want the point-slope equation of the line with y-intercept +4 and through the point (1, -1).

Solution

The graph shows you the line decreases 5 units from +4 to -1 as x increases 1 unit from 0 to 1. This tells you the slope is ...

m = rise/run = -5/1 = -5

The y-intercept is the value of y where the line crosses the y-axis:

b = 4

These values go into the point-slope equation:

y = mx +b . . . . . . line with slope m and y-intercept b

y = -5x +4 . . . . . . line with slope -5 and y-intercept 4