The complete graph of y=f(x), which consists of five line segments, is shown in red below. (On this graph, the distance between grid lines is 1.)

What is the sum of the -coordinates of all points where f(x)=1.8?

mathtoo Dec 25, 2018

#1**+2 **

The equation of the line joining (0, 0) and (1, 2) is

y = 2x

So when y = 1.8 x = .9

The equation of the line joining (1, 2) and (2, 1) is

y = -(x - 1) + 2

y = -x + 3

So.....when y = 1.8

1.8 = - x + 3

-1.2 = -x

1.2 = x

The equation of the line joining (2, 1) and (3, 3) is

y = 2(x -3) + 3

y = 2x - 6 + 3

y = 2x - 3

When y = 1.8

1.8 = 2x - 3

4.8 = 2x

2.4 = x

I assume you want the sum of the x coordinates when y = 1.8???

If so...we have

.9 + 1.2 + 2.4 =

4.5

CPhill Dec 25, 2018