Question

Solve the equation by completing the square round to the nearest hundredth is necessary x^2-x-7=0

Answer 1

The answers are 3.19 or -2.19.

In order to complete the square, you must first get the constant to the other side of the equation. WE do that by adding 7 to both sides.

x^2 - x - 7 = 0

x^2 - x = 7

Now we must take half of the x coefficient (-1), which would be -.5. Then we square it and add it to both sides. This is the second step to any completing the square problem.

x^2 - x = 7

x^2 - x + .25 = 7.25

Now that we have done that, the left side will be a perfect square so that, we can factor it.

x^2 - x + .25 = 7.25

(x - .5)^2 = 7.25

After having done that, we can take the square root of both sides

(x - .5)^2 = 7.25

x - .5 = +/-$\sqrt{7.25}$

Now we can take the value of that square root and solve.

x - .5 = +/-$\sqrt{7.25}$

x - .5 = +/-2.69

x = .5 +/- 2.69

And with the + and - both there, we need to do both to get the two answers.

.5 + 2.69 = 3.19

.5 - 2.69 = -2.19