Question

Help!! I'm confused with this one and I don't get it.

x(x+6)=9
What's the solution?

Answer 1

x=3

Answer 2

you use the distributive property to get

x^2 + 6x = 9

now you use completing the square

Answer 3

\[
\begin{align}
x(x+6)&=9\\
x^2+6x&=9\\
x^2+6x-9&=0
\end{align}
\]
Complete the square and solve.

Answer 4

\[\large x^2+6x-9=0\]

Answer 5

Yeah. What's the factors?

Answer 6

\[\huge\ x=-3\]

Answer 7

Because it can't be (x+3) (x-3)

Answer 8

It's wrong if you check it

Answer 9

Have you learned how to complete the square, @chol ?

Answer 10

I'm confused. If I use (x+3) (x-3) it would be x^2-9 only.

Answer 11

you can NOT use factoring. you use completing the square..so don't transpose 9 :P

Answer 12

\[(x-3(\sqrt2-1))((x-3(-1-\sqrt2)\]

Answer 13

Oh what's that?

Answer 14

=0

Answer 15

those are the roots

Answer 16

Radicals? I hate Radicals!!!

Answer 17

lol G...show solutions!! :P

Answer 18

I don't actually understand the equation o.O

Answer 19

you have x(x-6) = 9

distribute x...

x^2 - 6x = 9

do you know how to use completing the square @chol ?

Answer 20

if u are not good at completing squares just use
\[\Large x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}\]

Answer 21

Oh. Ok. I'll try it now on my paper.

Answer 22

Quadratic formula works but it is good to know how to complete the square.

Answer 23

quadratic formula was derived from completing the square..and completing the square is more useful :) especially in later maths

Answer 24

Wait, I'm solving. I'll show later what I got

Answer 25

you guys seem to behave as if i have said "ur method is bad" lols

Answer 26

Not at all @AravindG, I just wouldn't recommend a person to skip completing the square in favor of the quadratic formula. It's important for her to learn how to complete the square.

Answer 27

kk

Answer 28

Oh My! What are you talking about guys? I'm getting more confused!

Answer 29

haha dont mind us :P just solve it hehe

Answer 30

Hey I got \[-3 \pm 6\sqrt{2}\] Check it please.

Answer 31

i gave u the answers before

Answer 32

hmm i think it should be \(3\sqrt 2\)

Answer 33

That is the final answer? The one you showed me earlier?

Answer 34

yes
let me give u the answer @nbouscal and @lgbasallote was speaking of
\[\Large (x+3)^2=18\]

Answer 35

@AravindG : Can you show it to me again? It's not clear. Your answer.

Answer 36

now u can handle it from there

Answer 37

\[\Large x+3= \pm \sqrt{18}\]
\[\Large x=\pm \sqrt{18}-3\]

Answer 38

did u understand?

Answer 39

Yeah. But why use it?

Answer 40

to get the solution !!

Answer 41

the solutions are easily got by this method