C12 Binomial Expansion Watch

Ellie.Ginger
Badges: 10
Rep:
?
#1
Report Thread starter 3 weeks ago
#1
f(x)=(a-x)(3+ax)^5

The first question is to find the first 3 terms and give them in the simplest form.

The second question is to find the exact value of a, given that the co-efficient of x is zero in the expansion of f(x)

Can someone pls help me with the second question
Posted on the TSR App. Download from Apple or Google Play
0
reply
mqb2766
Badges: 14
Rep:
?
#2
Report 3 weeks ago
#2
What did you get for the first part, as the 2nd should be simply setting the x coefficient to zero?
(Original post by Ellie.Ginger)
f(x)=(a-x)(3+ax)^5

The first question is to find the first 3 terms and give them in the simplest form.

The second question is to find the exact value of a, given that the co-efficient of x is zero in the expansion of f(x)

Can someone pls help me with the second question
0
reply
Ellie.Ginger
Badges: 10
Rep:
?
#3
Report Thread starter 3 weeks ago
#3
(Original post by mqb2766)
What did you get for the first part, as the 2nd should be simply setting the x coefficient to zero?
I got 243+405ax+270a^2 x^2
Posted on the TSR App. Download from Apple or Google Play
0
reply
mqb2766
Badges: 14
Rep:
?
#4
Report 3 weeks ago
#4
(a-x)(3+ax)^5
Did you multiply it by the first expression in brackets?
(Original post by Ellie.Ginger)
I got 243+405ax+270a^2 x^2
0
reply
Ellie.Ginger
Badges: 10
Rep:
?
#5
Report Thread starter 3 weeks ago
#5
(Original post by mqb2766)
(a-x)(3+ax)^5
Did you multiply it by the first expression in brackets?
oh I'm so sorry I didn't mention. We were asked to find the first 3 terms of (3+ax)^5 only. then in the second question only we had to use the entire f(x)
Posted on the TSR App. Download from Apple or Google Play
0
reply
mqb2766
Badges: 14
Rep:
?
#6
Report 3 weeks ago
#6
So what did you get for the linear term in the 2nd part?
(Original post by Ellie.Ginger)
oh I'm so sorry I didn't mention. We were asked to find the first 3 terms of (3+ax)^5 only. then in the second question only we had to use the entire f(x)
0
reply
Ellie.Ginger
Badges: 10
Rep:
?
#7
Report Thread starter 3 weeks ago
#7
(Original post by Ellie.Ginger)
I got 243+405ax+270a^2 x^2
This
Posted on the TSR App. Download from Apple or Google Play
0
reply
mqb2766
Badges: 14
Rep:
?
#8
Report 3 weeks ago
#8
Eh?
The expansion of (3+ax)^5 is
243+405ax+270a^2 x^2
Multply that by (a-x)
What is the linear "x" term?

(Original post by Ellie.Ginger)
This
0
reply
Ellie.Ginger
Badges: 10
Rep:
?
#9
Report Thread starter 3 weeks ago
#9
(Original post by mqb2766)
Eh?
The expansion of (3+ax)^5 is
243+405ax+270a^2 x^2
Multply that by (a-x)
What is the linear "x" term?
I don't know how to do the second part of the question... so idk
Posted on the TSR App. Download from Apple or Google Play
0
reply
mqb2766
Badges: 14
Rep:
?
#10
Report 3 weeks ago
#10
Expand
(a-x)*(243+405ax+270a^2 x^2)
and collect terms (constant, linear, quadratic, ...).

(Original post by Ellie.Ginger)
I don't know how to do the second part of the question... so idk
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • Manchester Metropolitan University
    Undergraduate Open Day Undergraduate
    Wed, 19 Jun '19
  • University of West London
    Undergraduate Open Day - West London Campus Undergraduate
    Wed, 19 Jun '19
  • University of Warwick
    Undergraduate Open Day Undergraduate
    Fri, 21 Jun '19

How did your AQA A-level Biology Paper 2 go?

Loved the paper - Feeling positive (449)
18.96%
The paper was reasonable (1105)
46.66%
Not feeling great about that exam... (520)
21.96%
It was TERRIBLE (294)
12.42%

Watched Threads

View All