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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 x-coordinates of all points where f(x) = 1.8?

 

 Nov 27, 2020
 #1
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+1

Only two places  where f(x)  =  y   =1.8

 

Leftmost lsegment contains the points   ( -3,0)  and (-5, 4)

Slope  = [ 4 - 0] / [ -5 - -3]  =    4 / -2  =  -2

Equation  of the line  containing this segment

y = -2 ( x +3)

1.8  = -2 (x + 3)

-9/10 = x + 3

-9/10 - 3  = x

-9/10 - 30/10  = x

(-39/10)  = x   = -3.9     because of  symmetry, x = 3.9  is another solution

 

The sum of the x coordinates   =  0

 

cool cool cool

 Nov 27, 2020

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