Solve the equation by completing the square.
-$$3 x ^ { 2 } + 21 x = - 36$$
A) $$\pm \frac { 1 } { 2 }$$
B) $$- 4 , - 3$$
C) $$\pm \frac { 1 } { 2 } \mathrm { i }$$
D)3, 4

Question

Quizplus · Accepted Answer

First, divide the entire equation by 3 to simplify: $x^2 + 7x = -12$. Then, complete the square by adding $(\frac{7}{2})^2 = \frac{49}{4}$ to both sides: $x^2 + 7x + \frac{49}{4} = \frac{1}{4}$. This gives $(x + \frac{7}{2})^2 = \frac{1}{4}$. Solving for $x$, we find $x = -4$ and $x = -3$.

Solve the Equation by Completing the Square 3x2+21x=−363 x ^ { 2 } + 21 x = - 363x2+21x=−36

Solve the Equation by Completing the Square $3 x ^ { 2 } + 21 x = - 36$