Question

What value is added to both sides of the equation x2 − 2x = 10 in order to solve by completing the square?

−2
−1
1
2

Answer 1

@freckles

Answer 2

@amistre64 @dan815

Answer 3

what does it mean to complete a square?

Answer 4

ummmm i have no idea ... ._.

Answer 5

My math teacher's got a cool way to do this. Let me see if I can find a picture.

Answer 6

I'm pretty sure it'd be (-b/2a)^2

Answer 7

hmm, well it means that we want to create a perfect square out of what we are given.

say we are given the number 5, is it a perfect square?

if not, then what would we add to it to complete the square?

Answer 8

(a+b)^2 is a perfect square, it expands to a trinomial. can you expand it for me?

Answer 9

(a +b)(a+b)

?

Answer 10

yes (a+b)(a+b)

what does it look like when we expand it all out to a sum of 3 terms?

Answer 11

(a^2 + b)b

?

Answer 12

lol wait no.. idk .-.

Answer 13

you are going to have to remember how to multiply 2 binomial expressions ... either foil it out or just distribute ... but i cant do it for you.

Answer 14

is it a^2 +2ab + b^2

Answer 15

thats it :)

Answer 16

okok lol bad memory ._.

Answer 17

now that form is a 'complete' square

lets compare it to what we have

a^2 + 2ab + b^2
x^2 -2x

let a=x

x^2 + 2b x + b^2
x^2 -2x

when does -2x = 2b x? for what value of b?

Answer 18

-1 ?

Answer 19

idk if thats what u asked.

Answer 20

yes, b=-1

now you should notice that in order to complete our square, we have to add b^2 to the setup ..

what is (-1)^2 ?

Answer 21

1

Answer 22

good

x^2 - 2x + (-1)^2
x^2 -2x ^^^^
add this part to complete the square.

so yes, add 1 to each side.

Answer 23

So answer is c.. thank you ^-^

Answer 24

good luck :)