The area of square ABCD is 7cm

We know that the area of a square of sidelength L, is:

Area = L^2

In this case, we have:

L = 2cm + x cm

And we know that the area of the square is 7cm, then:

Area = 7cm^2 = (2cm + x cm)^2

7cm^2 =  4cm^2 + 4cm*xcm + (x cm)^2

7cm^2 = 4cm^2 + (4*x)cm^2 + x^2 cm^2

Now we can remove all the "cm^2" and just get the numbers:

7 = 4 + 4*x + x^2

We can subtract 4 in both sides to get

7 - 4 = 4 + 4*x + x^2 - 4

3 = 4*x + x^2

This is what whe wanted to prove.

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step-by-step explanation:

the first domain and range set to the left is matched with the top relation, and the second set the set in the middle goes with the bottom relation.