Question

7x^2=28

Answer 1

Start by isolating the x^2.

Answer 2

Not the 7x^2, but the x^2. So what do you get?

Answer 3

49x=28

Answer 4

or do i subtract the 7 on to the right side

Answer 5

x^2=28-7

Answer 6

you can't subtract the 7...

On the left, you have 7 multiplied by x^2. You need to divide both sides by 7.

Example: Isolate the "2" on the left side.
(5)(2) = 10 --->>> (5)(2)/(5) = (10)/(5)
2 = 10/5

Answer 7

So, try again... isolate x^2 on the left:

7x^2=28

Answer 8

thank you

Answer 9

x^2=4

Answer 10

great!

so x squared = 4... what is x?

Answer 11

try substituting the value of x to the original equation to check.. i kinda think it's wrong..

Answer 12

2

Answer 13

im so confused!

Answer 14

mostly right :)

Also, when x = -2, then x^ = 4 and the original equation 7(-2)^2 = 28

Answer 15

I apologize for my intrusion...i think you should cancel the degree first by finding the square root of both sides...

Answer 16

No, you got half of the answer fine :)

You just need to realize that x^2 = 4 leads to two different solutions, both x = 2 and x = -2. That's not an error... it is supposed to be like that :)

This is @darkprince14's point, I think?

Answer 17

so from the equation
7(-2)^2 = 28
(-14)^2 = 28
\[196\neq28\]

Answer 18

so the answer is {-2,2}

Answer 19

@JakeV8 pls correct me if i'm wrong..

Answer 20

i dont think you sqrt 7 7(-2)^2=28

Answer 21

well, the danger in doing the sqrt is that sqrt is only good for positive x values. You "lose" the x=-2 solution by taking sqrt of both sides.

Answer 22

not if its in multiple choice :P

Answer 23

the equation 7x^2 = 28 is in the form of ax^2..
so the vertex must be at the point of origin...
that's what i know.. is this right??

Answer 24

Ok, I was wrong about that graph, this isn't an x-y problem.

Here's the solution to reduce our collective confusion.
7x^2 = 28
x^2 = 4
x^2 - 4 = 0
(x+2)(x-2) = 0
Solutions are at x = -2, x = 2.

Answer 25

okay...i got the picture..thanks

Answer 26

Glad to help. In fact, I have seen someone else get the question specifically of "Why can't you just take the square root of both sides?" and the above solution illustrates why you shouldn't.

Answer 27

thank you guys for your help. I have tons more I need help with!

Answer 28

thats ok we are all learning. And its good you put it out there.

Answer 29

wrong typo..XD..

Answer 30

it really does help me understand the problem better which way is best which should i avoid things in that matter.