Harlon wrote the equation A=18 (x^2+1) to find the area of a rectangle that has a length of x^2+1 and a width of 18. He solved for x and got x = ±√ (A/18 - 1). Which of the following is an equivalent equation for x?

A. x = ±√ (A-18/18)

B. x = ±√ (A+18/18)

C. x = ±√ (A-36)

D. x = ±√ (A+36)

To solve for x in the equation for the area which was given to be, A = 18 (x^2 + 1), we divide both sides of the equation by 18 first.

A/18 = x^2 + 1

Then, we subtract 1 from both sides of the equation,

A/18 - 1 = x^2

Then, we simplify the expression in the left side of the equation,

(A - 18) / 18 = x^2

And finally, obtain the square root from both sides of equation,

Sqrt ((A-18) / 18) = x

The expression equivalent to this is letter A.