Question

Solve the following equation by first writing the equation in the form a x squared = c:

3 a squared minus 21 = 27
A. a = 4
B. a = plus-or-minus 4
C. a = plus-or-minus 16
D. a = 16

Answer 1

9514 1404 393

Answer:

B. a = plus-or-minus 4

Explanation:

3a² -21 = 27 . . . . . . . given

3a² = 48 . . . . . . . . . . add 21 to both sides (desired form)

a² = 16 . . . . . . . . . . . divide both sides by 3

a = ±4 . . . . . . . take the square root