Question

can someone plz help me in surds

Answer 1

\[\frac{ 3+2\sqrt{5} }{ 2\sqrt{5}-1} \times \frac{ 2\sqrt{5}+1 }{ 2\sqrt{5}+1} \]

Answer 2

the answer is \[\frac{ 8\sqrt{5} +23}{ 20 -1 }\]

Answer 3

that negative 1 i cant get

Answer 4

its rationalising the denominator

Answer 5

This looks so tedious...

Answer 6

Or not.
Exactly why can't you get that -1?

Answer 7

no how do u solve just \[(2\sqrt{5}-1) \times (2\sqrt{5} +1)\]

Answer 8

The same way you solve
(2x - 1)(2x + 1)
It should yield a difference of two squares :D
\[\Large (a -b)(a+b) = a^2 - b^2\]

Answer 9

i tried not working the answer i s\[20 -4\sqrt{5} +1\]

Answer 10

oh wait srry i was thinking \[a ^{2}-2ab+b\]

Answer 11

You might have to rethink your FOIL method...
\[\Large (2\sqrt 5 \color{blue}- 1)(2\sqrt 5 \color{red}+ 1)\]
XD

Answer 12

You thought of it as a square of a binomial? XD

Answer 13

thank u

Answer 14

No sweat ^^

Answer 15

so when to know to use bionomail or that rule

Answer 16

If they share the same sign.
\[\Large (2\sqrt5 - 1)(2\sqrt 5 - 1) = 20 - 4\sqrt5 + 1 = 21 - 4\sqrt 5\]
It's highly unlikely, as you're multiplying conjugates... the purpose of which is to get rid of that bloody radical :D

Answer 17

thank u again