!!20 points and Brainliest!!!! Make sure to explain!!!
Which of the following would best be solved using completing the square?
A) 2x^3 - 12x^2 + 5x - 30 = 0
B)5x^2 + 7x = 12
C) x^2 = 81
D) x^2 + 4x - 21 = 0
