Year 12s: what will be the first way you research your future options? >>

GCSE Surds Question

2x59

(edited 8 years ago)

Reply 1

math42

No. Show your working?

Reply 2

Turtlebunny

Not too sure how you get 48.
Please show your full workings so I can help you further.

The answer is 30+10√3. Here's how you get it.

√75*√75 = 75 - Finding the square root of 75^2 will simply take you back to 75, should know this.
To do √75 * -√27, you would need to simplify these two surds, as in a non-calc paper, I would not want to be doing this calculation.
As such:
√75 simplifies to 5√3 - because √25 * √3 = √75 and the √25 = 5.
-√27 simplifies to -3√3 because √9 * √3 = √27 and the √9 = 3

So then 5√3 * -3√3 = (5*-3)+(√3*√3) = -15*3 = -45
Then, √25 = 5. So 5*5√3 = 25√3.
5*-3√3 = -15√3.

75-45 = 30
25√3 -15√3 = 10√3.

This should be fairly straightforward with correct, neat working. If you need some help on surds and wish to talk on skype, PM me.

Reply 3

ko111

Original post by Turtlebunny

not allowed to post full answers its against the rules instead guide the original poster to the right direction.

Reply 4

Turtlebunny

Original post by ko111

not allowed to post full answers its against the rules instead guide the original poster to the right direction.

Then how otherwise is he able to learn from it? It's his own pitfall if he chooses to take the answer, and not work through what I laid out - he will be the one who is suffering. I did not give a direct answer, and included an explanation as to how you reach the final thing.

Reply 5

math42

Original post by Turtlebunny

Obviously worked solutions can be valuable to look at but by offering one so quickly you kind of deny her the arguably greater rewards from working through a correct solution independently
Of course at GCSE with a problem like this that's not a huge deal but in general it's frowned upon

Reply 6

TenOfThem

Original post by 2x59

I needed an answer rather than help in this case but thank you.

There are plenty of sites that just provide answers ... This site is not intended to be one of them

Reply 7

Chittesh14

The easiest way is to split the number up into their simplified form. Like root 75 can be written as root 25 * root 3 = 5(root 3)
Full solutions are not allowed to be posted therefore we can only give you clues. However, the way to answer these questions is always simplify the surds hence why the question said simplify :P. Usually, people just multiply the surds and come up with an answer like root 3500 etc.