One side of the square was reduced by 3 cm, and the other was enlarged 2 times. The area of the resulting rectangle is 40

One side of the square was reduced by 3 cm, and the other was enlarged 2 times. The area of the resulting rectangle is 40 square cm. What was the side length of the original square.

Since the sides of the square are equal to each other, we take the initial length of its side as x.

After one of the sides was reduced by 3 cm, it was: x – 3 cm.

After the friend was enlarged 2 times, it was: 2 * x.

The area is the product of the sides of the figure, so we get the following equation:

2 * x * (x – 3) = 40.

2 * x ^ 2 – 6 * x = 40.

x ^ 2 – 3 * x = 20.

We get a quadratic equation:

x ^ 2 – 3 * x – 20 = 0.

D ^ 2 = 9 – 4 * 1 * (-20) = 89.

D = 9.44.

x = (3 + 9.44) / 2 = 6.22 cm.

Answer:

6.22 cm.