Find the truth set of the equation x2 = 3(2x + 9)
-
A.
{x : x = 3, x = 9} -
B.
{x : x = -3, x = -9} -
C.
{x : x = 3, x = -9} -
D.
{x : x = -3, x = 9}
Correct Answer: Option D
Explanation
x2 = 3(2x + 9)
x2 = 6x + 27
x2 – 6x – 27 = 0
x2 – 9x + 3x – 27 = 0
x(x – 9) + 3(x – 9) = (x + 3)(x – 9) = 0
x + 3 = 0 or x – 9 = 0
x = -3 or x = 9
x = -3, x = 9