Answer: x = 2.5
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Step-by-step explanation:
The rectangle on the left has area of length*width = 4x
The rectangle on the right has an area of x(2x+3) = 2x^2+3x
Combining those two sub areas gets us a total area of 4x+2x^2+3x = 2x^2+7x
Set this equal to the stated area of 30 square mm and get everything to one side.
2x^2+7x = 30
2x^2+7x-30 = 0
Compare this with the template ax^2+bx+c = 0 to find that
We'll plug these values into the quadratic formula like shown below.
A negative x value doesn't make sense in this context. It's not possible to have a negative length or negative width. So we'll simply ignore x = -6 and go with x = 2.5 as the final answer
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Check:
The rectangle on the left has area of A = 4x = 4*2.5 = 10 square mm.
The rectangle on the right has area B = x*(2x+3) = 2.5*(2*2.5+3) = 20 square mm
The total area is A+B = 10+20 = 30 square mm which matches with what the instructions mentioned. The answer is confirmed.