Binomial Theorm (1 Viewer)

[ghostman_on_3rd]

hello, i need help with this question:

Find the greatest term in (5-4x)^12, if x = 2/3


Books answer: 12C4 (5^8)(8^4)(3^-4)
My answer: 12C5 (5^7)(-8^5)(3^-5)

 

[lyounamu]

hello, i need help with this question:

Find the greatest term in (5-4x)^12, if x = 2/3


Books answer: 12C4 (5^8)(8^4)(3^-4)
My answer: 12C5 (5^7)(-8^5)(3^-5)

greatest term is when: (n-r+1)/r x b/a

(13-r)/r x (8/3)/5 > 1
104 - 8r > 15r

23r < 104
r < 4.xxx

r =4 i.e. 5th one...
HOWEVER, since the sign becomes negative with that, we have to use 4th one.

 

[Divinity_]

greatest term is when: (n-r+1)/r x b/a

(13-r)/r x (8/3)/5 > 1
104 - 8r > 15r

23r < 104
r < 4.xxx

r =4 i.e. 5th one...
HOWEVER, since the sign becomes negative with that, we have to use 4th one.

i got that too

 

[ghostman_on_3rd]

greatest term is when: (n-r+1)/r x b/a

(13-r)/r x (8/3)/5 > 1
104 - 8r > 15r

23r < 104
r < 4.xxx

r =4 i.e. 5th one...
HOWEVER, since the sign becomes negative with that, we have to use 4th one.

o i c, you didnt bother with the negative in -4x/5 x = 2/3