## Jeans123 3 years ago solve the quadratic equation by comleting the square, x^2-12x+7=0

1. ivanmlerner

Sum 29 on both sides and you get:$x^2-12x+36=(x-6)^2=29$Do square root, isolate x and you get your answer.

2. Jeans123

huh?

3. Jeans123

Where did you get 29 from?

4. ivanmlerner

(a+b)^2=a^2+2ab+b^2 To complete the squares is to go from something like the right part to something on the left side. a in this case is clearly x, and because of the second term, we know that b is 6, but we only have 7 on the place of b² and we need to have 36. What is missing for we to get 36 is what we need to add, wich is 29.

5. yummydum

k i know im late on this but ill explain it anyway... $x^2-12x+7=0$we're gonna complete the square for this first move the $$7$$ over to the other side:$x^2-12x=-7$now fill in the following blanks with the square of half the middle term [$$({12\over2})^2$$]:$x^2-12x+\text{___}=-7+\text{___}$$x^2-12x+36=-7+36$now combine like terms:$x^2-12x+36=29$next write the simplified version of $$x^2-12x+36$$ which is $$(x-6)(x-6)$$=$$(x-6)^2$$:$(x-6)^2=29$square root both sides:$x-6=\sqrt{29}$add 6 to both sides:$\large x=6\pm\sqrt{29}$ hope you get how to do this now! :) ...sorry it was so late