solve the equation by completing the square. Round to the nearest tenth.
x^2 + 8x = 10

A. 1.1, 9.1
B. 1.1, -9.1
c. -1.1, 9.1
D. -1.1, -9.1

Respuesta :

B.
1.1, -9.1

[tex] x^{2} +8x=10[/tex]

Answer:  The correct option is (B) 1.1, -9.1.

Step-by-step explanation:  We are given to solve the following quadratic equation by the method of completing the square.

[tex]x^2+8x=10~~~~~~~~~~~~~~~~(i)[/tex]

In completing the square method, we need to make left hand side of the above given equation as a perfect square trinomial.

From equation (i), we have

[tex]x^2+8x=10\\\\\Rightarrow x^2+2\times x\times 4+4^2=10+4^2\\\\\Rightarrow (x+4)^2=10+16\\\\\Rightarrow (x+4)^2=26\\\\\Rightarrow x+4=\pm\sqrt{26}\\\\\Rightarrow x=-4\pm \sqrt{26}\\\\\Rightarrow x=-4\pm 5.09\\\\\Rightarrow x=-4+5.09,~~~~~x=-4-5.09\\\\\Rightarrow x=1.09,~~~~~~~~~\Rightarrow x=-9.09.[/tex]

Rounding to the nearest tenth, we get

[tex]x=1.1,~~-9.1.[/tex]

Thus, the required solution is x = 1.1, -9.1.

Option (B) is CORRECT.