Question

quadratic equations help
this is the process of completing the square by the way....

x+8 = +- √ 121
the +- is a plus or minus sign

then it simplifies to x+8 = +- 11

so now what you'd do is subtract 8 from both sides so it's x= -8 +- 11
but why don't you subtract 8 from 11? and why do we have to have a +- sign with radicals?

if this question does make sense go here http://www.youtube.com/watch?v=gzm-uhj06q8&feature=relmfu
at 06:00

Answer 1

i meant if this equation doesn't make sense

Answer 2

in the last sentence

Answer 3

Khan Academy? Hmm That seems reliable

Answer 4

what do you mean?

Answer 5

Ah doesnt :P lol Nvm

Answer 6

but still... why don't you subtract 8 from 11?

Answer 7

Well, when you get + - 11 and you have to add 8 to it, it leads to 2 answers
+ 11 - 8
-11 - 8

Radicals have + - because if you square
+11 x +11 = 121
-11 x -11 = 121

Answer 8

wait so in 9 +- 3 √ 33 over -18, why do you divide evertying by 3 intstead of adding/subtracting it to 9?

Answer 9

Oh because 9, (+-) 3, and 18 have a common multiple of 3
9/3 = 3
3/3 = 1
18/3 = 6

Answer 10

but why can't you add 9 to 3?

Answer 11

is it because it's being multiplied by a radical?

Answer 12

Because it is 3 has a radical with it..You need the same randical on both terms to complete an operation =) Yes

Answer 13

wait so... why are you able to divide it?

Answer 14

Only if the bottom denominator has a radical, you can't divide it..But since it is an alone constant, you can =)

During addition or substraction you cant..
Like
3 +- 3 square root 5
-----------------
12
is equal to
1 + - 1 square root 5
-----------------
4

Answer 15

thanks, do you learn this when you learn dividing radicals?

Answer 16

Anytime =)

Divinding radicals is a different concept

Answer 17

oh wait please then ... can you put what you said in kid friendly terms because i don't fully understand sorry

Answer 18

Which part?

Answer 19

like, how is 3 +- 3 square root 5
-----------------
12
is equal to
1 + - 1 square root 5
-----------------
4

Answer 20

Well, you see all of them have a common multiple..
3 can be divided by 12 to be
3/12 = 1/4

(+-)3/12 = (+-) 1/4

Now just fill in the blanks
1 + - 1 sqaure root 5
----------------
4

Answer 21

ok so back to 9 +- 3 √ 33 over -18
the only reason you divided is to simplify it?

Answer 22

nevermind... i need to relearn adding and multiplying radicals

Answer 23

Yep to simplify it =)

Answer 24

That'd help =)