If a( x, 1), b( -3,7), c( -5, 9), and d( 5, 4), find the value of x so that line ab is parallel to line cd.

The slope of CD = (9-4) / (-5-5) = 5/-10 = -1/2

The slope of AB must also be -1/2

Slope of AB = (1-7) / (x - -3) = -6 / (x+3)

For AB to equal -1/2, the denominator needs to be twice as much as the numerator, so set up an equation:

2(x+3) = 12

Now solve for x:

2x +6 = 12

2x = 18

x = 18/2

x = 9

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step-by-step explanation: