Question

Use the expansion of (2-x)^5 to evaluate (1.98)^5, correct to 5 d.p

Answer 1

1.98 = (2-0.2)

Answer 2

ok..

Answer 3

so u can solve it now?

Answer 4

What do I need to do

Answer 5

You have a formula for (x-y)^5 ?

Answer 6

u can also write it as (2-0.02)^5
which is (2-0.02)^2 * (2-0.02)^2 * (2-0.02)

Answer 7

right?

Answer 8

why ^2

Answer 9

Total power is five.
You divide the powers into 2, 2 and 1

Answer 10

ok

Answer 11

@Brainybeauty

Answer 12

@OOOPS

Answer 13

do you know Pascal's triangle?

Answer 14

That's a longer method

Answer 15

ok, so you want taking Brainy beauty 's one as above?? just apply

Answer 16

Yes.. but how

Answer 17

you have 3 terms, right? first 2 terms are the same (2-0.02)^2
hehehe it is (a-b)^2 = a^2 -2ab +b^2 , your a =2, your b = 0.02, just apply to get (2-0.02)^2

Answer 18

\[(\color{red}{a}-\color{blue}{b})^2=\color{red}{a^2}-2*\color{red}{a}*\color{blue}{b}+\color{blue}{b^2}\\(\color{red}{2}-\color{blue}{0.02})^2=\color{red}{2^2}-2*\color{red}{2}*\color{blue}{0.02}+\color{blue}{0.02^2}\]

Answer 19

you do the rest, please.

Answer 20

Okay! Got it!

Answer 21

Thank you @Brainybeauty and @OOOPS