Solve for x.
8x^2-5=11

Question

Solve for x.
8x^2-5=11

moonlitfate · Answer

All right!  Do you know what the first step to solving the equation would be at all?

anonymous · Answer

nope !:(

moonlitfate · Answer

Basically, what you're going to do is try isolate x (get it by itself) in order to solve for it.

anonymous · Answer

alright, and i get to but i dont know what kind of two they have weird answer choices for me?

anonymous · Answer

2*

anonymous · Answer

is it +-2 or the square root =-2?

moonlitfate · Answer

$$8x^2 - 5 = 11$$

Add 5 to both sides of the equation to isolate x:
$$8x^2-5(+5) = 11 +5$$
The 5 on the left will cancel out leaving you with:$$8x^2 = 16$$
$$x^2 = 16$$
$$x = \sqrt{16}$$
$$x = 4$$

moonlitfate · Answer

Oh wait, I skipped a step; sorry. x.x It should be....

anonymous · Answer

alright but all my choices have to do with a 2

anonymous · Answer

wait no they dont so its 4?

moonlitfate · Answer

No, I skipped a step; so ignore that for now.

moonlitfate · Answer

$$8x^2 = 16$$
$$x^2 = 2$$
$$x = \sqrt{2}$$

moonlitfate · Answer

Is it asking for two answers, though?

anonymous · Answer

nope just one thank you so much its the squear root of two?

moonlitfate · Answer

$$\pm \sqrt{2}$$ ; you can't have a negative under a radical; since that would be a completely different concept of Algebra. :p

anonymous · Answer

what about this one:

What constant term should be used to complete the square?

x^2 - 5x + _____ = 7

moonlitfate · Answer

Let me see if I can remember this, been a while. :)

moonlitfate · Answer

$$x^2-5x+ ? = 7$$
What you're going to take the middle term of your polynomial divide it by 2 and square it, if that makes sense.

moonlitfate · Answer

So the first step:

moonlitfate · Answer

$$x^2-5x+\frac{ 10 }{ 4 }=7$$

anonymous · Answer

alright ...got it

moonlitfate · Answer

Since you added 10/4 on the left, you're going to same on the right. $$x^2-5x+\frac{ 10 }{ 4 }=7+\frac{ 10 }{ 4 }$$

moonlitfate · Answer

x^2-5x+10/4 = 38/4
$$(x-\frac{ 5 }{ 2 })^2=\frac{ 38 }{ 4 }$$

moonlitfate · Answer

@exzaireah -- Is this helping at all? :x

anonymous · Answer

yes im understandin just not any of my answer choices.

moonlitfate · Answer

What are the choices given to you?  Just to make sure I'm doing this correctly;  I don't want to confuse you by doing the wrong thing.