Can 8xcubed = y cubed simplfy to 2x = y?

  • 0 votes

I had a question like this in my last maths paper and I'm wondering whether this is correct. 

Posted Tue 12th June, 2012 @ 20:59 by Terrie

3 Answers

  • 1 vote

No u cannot simplify that because at the moment you have y=8x^3 and when you cube root this equation u get cube root y= 2x

because wot u do to one side u must do to the other !!

Answered Mon 18th June, 2012 @ 22:31 by Braniac
  • 0 votes

You can't simplify it. It only works with 1. If you try x=2, with 8xcubed y=64 but with 2x, y=4. It doesn't work with other numbers as well. I can't remember the reason why it doesn't work but don't just sub 1 into the two equations. use a range of numbers because in this case it shows that it doesn't work.

You could simplify it to (2x)^3 because when you expand the brackets you get 2^3 = 8 and x^3.

Answered Wed 13th June, 2012 @ 17:24 by Sophie
Edited by Sophie on Thu 21st June, 2012 @ 18:06
  • -1 votes

Yes this is correct. If you simplify an equation and you're not sure if you've done it right, substitude a couple of values for x in to see if it's right. For example using your question sub in x=1, 8xcubed= 8 so y=2  and then sub x=1  into your simplified equation and if you get the same value for Y then it is right(your simplified equation also gives Y=2 ).

Answered Wed 13th June, 2012 @ 12:53 by Amanda