Nataliebain
New member
- Joined
- Oct 25, 2014
- Messages
- 3
I'm really not sure where to post this, I have just started a home learn A level course and I'm a bit rusty
Here are a few things I cannot get my head round ...
(3√2+5√3)^2 = (3√2+5√3)(3√2+5√3)
= 3√2(3√2+5√3)+5√3(3√2+5√3) - I get that we are multiplying what's outside the brackets with what's inside.
= 9√4+15√6+15√6+25√9 - I get that we can add the two 15√6 to make it 30√6
= 18+30√6+75 - Why has the 9√4 and the 25√9 been multiplied by 3?? Also why has the √9's disappeared?
I realise I'm probably being a bit thick but I haven't done maths in a while so this is really annoying me!
Also
5-√75/-5 = 5-√25x3/-5
= 5-5√3/-5 - I understand how I'm getting to here
= 5(1-√3)/-5 - why has the -5 on top
turned into 1-?? I'm guessing we have divided something? Why and what?
= √3-1 - why has the -1 moved and what has happened to get rid of the 5 and the -5?
I know this is simple but I cannot fathom this out??
Here are a few things I cannot get my head round ...
(3√2+5√3)^2 = (3√2+5√3)(3√2+5√3)
= 3√2(3√2+5√3)+5√3(3√2+5√3) - I get that we are multiplying what's outside the brackets with what's inside.
= 9√4+15√6+15√6+25√9 - I get that we can add the two 15√6 to make it 30√6
= 18+30√6+75 - Why has the 9√4 and the 25√9 been multiplied by 3?? Also why has the √9's disappeared?
I realise I'm probably being a bit thick but I haven't done maths in a while so this is really annoying me!
Also
5-√75/-5 = 5-√25x3/-5
= 5-5√3/-5 - I understand how I'm getting to here
= 5(1-√3)/-5 - why has the -5 on top
= √3-1 - why has the -1 moved and what has happened to get rid of the 5 and the -5?
I know this is simple but I cannot fathom this out??