Question

Help on completing the square..

Answer 1

im pretty sure the answer is \[\sqrt{19}-4\]

Answer 2

You can check your answer by using the quadratic formula (the quadratic formula is derived by completing the square).

Answer 3

okay ill do that

Answer 4

First i group together the x terms, then add 3 to both sides \[\Large (x^2+8x) -3 = 0\] add 3 to both sides \[\Large (x^2+8x) = 3\] then just divide the 8 by 2, that's what goes in the brackets \[\Large (x+4)^2 = 3 + 16\] add 16 to the right because we're adding 4^2 on the left

Then take square root, and subtract 4 on both sides \[\Large x=\sqrt {19}-4\]

Answer 5

kewl, that's exactly how my work looks. thx!

Answer 6

Excellent :)

You can do the middle step of adding in the 16 squared part beforehand, like this...
\[\Large (x^2+8x + 16) = 3 \]
but imo it's far easier to skip that step... just divide whatever's in front of the x by 2, put it in brackets, then see what number you're adding by squaring it (as long as the number in front of x^2 is 1, otherwise you have to divide that out first)