Solve by completing the square.?

Question

Solve by completing the square.
2x^2-8x-5=0

Answer 1

x² - 4x=5/2
x² - 4x +4=5/2+4
(x-2)²=√13/2 = √26/2
x=2±√26/2

Answer 2

Hi,
Well, since the coefficient of the x², 2, is not a perfect square, we need to get rid of the 2 in front of that term.
2x² -8x -5 =0 (Your equation.)
2x² -8x =5 (Add 5 to each side of the equality sign.)
x² -4x =5/2 (Divide all terms by 2.)
x²-4x +4 =5/2 +4 (Divide the coefficient of x by 2 (that's 2) and square that number, (2² =4), and add that squared number,4, to both sides. )
(x-2)² =5/2 +8/2 (Rewrite the left side as a perfect square and convert 4 to halves.)
x -2 = +- sqrt(13/2) (Add the numbers on the right and take the square root of both sides.)
x = 2 +- sqrt (13/2) (Add 2 to both sides.)

(Sorry, that the text is mixed into the problem steps, but this word processor is a little tedious to get a desired format.)

Incidentally, if the number in front of the x² term is a perfect square, it's usually easier to complete the square without dividing throught by that coefficient.

Hope this helps.
FE

Hope this helps.

Answer 3

I ask because I am really curious but what do you learn if someone else does this math problem for you?