Please help me find the value of x!

Exact     x = 16/3

Approximate      x = 5.333

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Work Shown:

base = 3x-1

height = x

area of triangle = (base*height)/2

40 = x*(3x-1)/2

40*2 = 3x^2 - x

80 = 3x^2 - x

0 = 3x^2 - x - 80

3x^2 - x - 80 = 0

Now apply the quadratic formula

A negative height doesn't make sense, so we ignore x = -5

The only solution is x = 16/3 which approximates to x = 5.333

d. it is a convex pentagon because it has five sides and none of the sides would extend into the inside of the polygon.

step-by-step explanation: