Final answer:
To find the positive value of x for the equation x^2 + 2x = 2(x + 8), we simplify and solve for x. After simplifying, we get x^2 = 16, and taking the square root of both sides, we find that x = 4, which is the solution.
Step-by-step explanation:
The student is asking for the positive value of x that makes the equation x^2 + 2x = 2(x + 8) true. To solve for x, we first expand the right side of the equation and then subtract all terms to one side to set the equation to zero:
x^2 + 2x = 2x + 16
We then cancel out the 2x on both sides:
x^2 = 16
Now we take the square root of both sides:
x = ±√16
Since we are looking for the positive value of x:
x = 4
Hence, the positive value of x that satisfies the equation is 4, which corresponds to option D.