Solve the quadratic equation 5x^2 -125 = 0.

Question

surana · Answer

The ^2 represents Exponent of 2.

michele_laino · Answer

hint:
$$5{x^2} - 125 = 5\left( {{x^2} - {5^2}} \right) = 5\left( {x - 5} \right)\left( {x + 5} \right)$$

surana · Answer

That'll help, thanks.

michele_laino · Answer

thanks!

surana · Answer

You're welcome.

michele_laino · Answer

thanks! :)

surana · Answer

I'm just going to solve it on a piece of paper and then come back with the answer.

thesmartone · Answer

Not a lot more work can be done on paper. :P

You just now have to set each one to 0, to find the roots (or the value of x) :)

anonymous · Answer

Not a lot more work can be done on paper. :P

You just now have to set each one to 0, to find the roots (or the value of x) :)

surana · Answer

Set to zero?

thesmartone · Answer

$\sf 5(x+5)(x-5)$

And then to find the value of x:

$\sf (x+5)=0$
and
$\sf (x-5)=0$

And solve for x in both equations, and you should have two values for x as your answer :)

anonymous · Answer

5(x+5)(x−5)

And then to find the value of x:

(x+5)=0
and
(x−5)=0

And solve for x in both equations, and you should have two values for x as your answer :)

surana · Answer

So I have to multiply x+5 by 5 and then put five on the side of x and then divide?

thesmartone · Answer

No, you just subtract 5 on both sides. And for the other equation, you add 5 to both sides. :)

anonymous · Answer

No, you just subtract 5 on both sides. And for the other equation, you add 5 to both sides. :)

surana · Answer

Thank you, I will work that out then.

surana · Answer

I got -5 and +5.

thesmartone · Answer

Correct. :)

So now if you wanted to test out those answers, then plug in x=5 and x=-5 into the original equation, and it would equal to 0! :)

michele_laino · Answer

that's right!

anonymous · Answer

uh yae

surana · Answer

So one of those two is the answer, I'll check, then.

michele_laino · Answer

both of those numbers are the answer

thesmartone · Answer

^

surana · Answer

The thing is that the answers I'm allowed is that only one of those can be chosen. I still don't know which one to choose.

surana · Answer

I think I'll go with -5.

thesmartone · Answer

Do you have answer choices? If the answer box is a blank then try putting `5, -5`

poopsiedoodle · Answer

is there a choice for $\pm$5?

surana · Answer

Yeah, there is.

michele_laino · Answer

is x a length?

surana · Answer

Does that mean both positive and negative?

poopsiedoodle · Answer

yes, it does

surana · Answer

Then I'll go with that one instead.

thesmartone · Answer

:)

surana · Answer

Thank you all!

surana · Answer

I'll close the question now.

poopsiedoodle · Answer

good luck with your future math things :*