Question

Find the value of a if (1+ax)^5= 1+20x+...
I think the value is 4, is this correct. If not how do you work it out?

Answer 1

Yes

Answer 2

@jamie123 any theory to it?

Answer 3

1+20x+... what is this

Answer 4

(1+ax)(1+ax)...5 times
in this ax would be repeated 5 times you get power of x as 1 only when ax is multiplied by 1 and this would happen 5 times, so 5ax = 20x, a=4

Answer 5

binomial expansion @aajugdar

Answer 6

x coefficient = \(\large \binom{5}{1}1^{5-1}a^1 = 5a\)
\(\large \implies 5a = 20 \implies a = 4\)

Answer 7

oh so you are comparing LHS's x coeficient to RHS's x coeficient

Answer 8

yeah thats what i thought...

Answer 9

haha
i was clueless about this,so should be correct