Question

Solve x2 = 12x – 15 by completing the square. Which is the solution set of the equation? (negative 6 minus StartRoot 51 EndRoot comma negative 6 + StartRoot 51 EndRoot) (negative 6 minus StartRoot 21 EndRoot comma negative 6 + StartRoot 21 EndRoot) (6 minus StartRoot 51 EndRoot comma 6 + StartRoot 51 EndRoot) (6 minus StartRoot 21 EndRoot comma 6 + StartRoot 21 EndRoot)

Answer 1

Answer:

the answer is d

Step-by-step explanation:

Answer 2

Answer:

LAST OPTION: $(6-\sqrt{21},6+\sqrt{21})$

Step-by-step explanation:

1. Subtract $12x$ from both sides of the equation:

$x^2-12x= 12x- 15-12x\\\\x^2-12x=-15$

2. Since $b=12$:

$(\frac{b}{2})^2=(\frac{12}{2})^2=(6)^2$

3. Now can complete the square. Add $(6)^2$ to both sides of the equation:

$x^2-12x+6^2=-15+6^2$

4. Simplifying:

$(x-6)^2=21$

5. Solve for "x":

$\sqrt{(x-6)^2}=\±\sqrt{21}\\\\x-6=\±\sqrt{21}\\\\x=6\±\sqrt{21}\\\\x_1=6+\sqrt{21}\\\\x_2=6-\sqrt{21}$

6. The solution set is:

$(6-\sqrt{21},6+\sqrt{21})$