Please help meee(urgentttt)!!

Watch this thread
blackmangotree
Badges: 11
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#1
Report Thread starter 1 year ago
#1
Guys i have to do this maths test and I literally have no idea what to do for ths question:

Expressions for consecutive triangular numbers are:
0.5n(n+1) and 0.5(n+1)(n+2)

prove that the sum of two consecutive triangular numbers is always a square number

thank you
0
reply
Pangol
Badges: 15
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#2
Report 1 year ago
#2
(Original post by blackmangotree)
Guys i have to do this maths test and I literally have no idea what to do for ths question:

Expressions for consecutive triangular numbers are:
0.5n(n+1) and 0.5(n+1)(n+2)

prove that the sum of two consecutive triangular numbers is always a square number

thank you
Since the question asks you to prove something about the sum of consecutive triangular numbers, try adding together the expressions you are given and see what you can make of that. This is the kind of question where it isn't easy to see how it's going to work out, you just have to get stuck in.

It is better to write the 0.5 as 1/2 in both cases. Don't expand any brackets, factorise instead.
0
reply
blackmangotree
Badges: 11
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#3
Report Thread starter 1 year ago
#3
(Original post by Pangol)
Since the question asks you to prove something about the sum of consecutive triangular numbers, try adding together the expressions you are given and see what you can make of that. This is the kind of question where it isn't easy to see how it's going to work out, you just have to get stuck in.

It is better to write the 0.5 as 1/2 in both cases. Don't expand any brackets, factorise instead.
what do you mean by don't expand any brackets? because surely you need to expand brackets to add them together right?
0
reply
Pangol
Badges: 15
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#4
Report 1 year ago
#4
(Original post by blackmangotree)
what do you mean by don't expand any brackets? because surely you need to expand brackets to add them together right?
Not at all. Suppose you were adding 2(x + 3)(x - 4) and 6(x + 3)(x + 1). Without expanding the brackets, you could do it like this:

2(x + 3)(x - 4) + 6(x + 3)(x + 1) = 2(x + 3)[(x - 4) + 3(x + 1)] (since both terms have a factor of 2 and (x + 3)

= 2(x + 3)[x - 4 + 3x + 3)] (now you can expand the brackets in the last term, since there is no choice left)

=2(x + 3)(4x - 1)

This gives a nicely factorised final answer, which is what you will need here.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
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

How did your AQA A-level Physics Paper 1 exam go?

Great! Feeling positive (139)
29.32%
It went fairly well (227)
47.89%
It didn't go too well (69)
14.56%
TERRIBLE! (39)
8.23%

Watched Threads

View All