Mathematics: Post your doubts here!

[Sarkerms]

Can anyone help me out with the b part of this Q. I have my exams tomorrow and I cant figure this out

 

[Maz]

Plz someone write the fully working for this and explain me!
It is October November 10 Paper 11!

Question number???

 

[littlecloud11]

Can anyone help me out with the b part of this Q. I have my exams tomorrow and I cant figure this out View attachment 22026

(ii) Any unit vector has a magnitude of 1. If AB is a unit vector |AB| = 1
AB = (k -k 2k) - (1 0 2) = (k-1, -k, 2k-2)
|AB| = √{(k-1)^2 + (-k)^2 + (2k-2)^2}
1 = √(k^2 -2k + 1 + k^2 + 4k^2 -8k +4)
1^2 = 6k^2 - 10k +5
1 = 6k^2 - 10k + 5
6k^2 -10k +4 =0
Solve and you get k as 1 and 2/3

 

[Sarkerms]

Can anyone help me with the ii part of this one as well

 

[josephsai]

pls help i can't solve 9709_w12_qp_31 question 2) 5^(x-1)=5^(x)-5

 

[gagandeep]

they already said leave the answer in surds..so when u do the equation x= -b ±√(b^2-4ac) / 2a u will end up with x =1/4 (-20 + √40) or 1/4(-20-√40) u can simplify it..did u get it now ?

the answer for this question is :
x= (-12+√40)/4 and x=(-12-√40)/4

 

[*MK*skydiver :D]

Can someone please help me in this :
Q1 Mechanics 2
http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_w09_qp_52.pdf
Thanks!

 

[soumayya]

pls help i can't solve 9709_w12_qp_31 question 2) 5^(x-1)=5^(x)-5

 

[josephsai]

View attachment 22061

thx u veryyyyyyy muchh.

 

[josephsai]

r

Question number???

its a lot

 

[HubbaBubba]

The amounts of money, x dollars, that 24 people had in their pockets are summarised by Σ(x − 36) = −60 and Σ(x − 36)2 = 227.76. Find Σx and Σx^2\

Does anybody have a guide on how to solve questions like these? They are really confusing :/

 

[Alice123]

Can any1 help with a(ii) ? thanks in advance

 

[Dug]

The amounts of money, x dollars, that 24 people had in their pockets are summarised by Σ(x − 36) = −60 and Σ(x − 36)2 = 227.76. Find Σx and Σx^2\

Does anybody have a guide on how to solve questions like these? They are really confusing :/

Sum of coded values = -60
Σx = -60 + (24*36) = 804

Σ(x-36)^2 = 227.76
Expand LHS:
Σ(x^2 - 72x + 1296) = 227.76
Σx^2 - 72Σx + Σ1296 = 227.76
We have Σx = 804 and Σ1296 = (1296)(24) = 31104
Σx^2 - (804)(72) + 31104 = 227.76
Σx^2 = 27011.76

 

[littlecloud11]

Can any1 help with a(ii) ? thanks in advance

5ai) For three courses a dish has to be picked from each course.
For the first course there are 3 options so 3C1
For the second course there are 5 options so 5C1. But each dish has two possible choices of being served with either fries or potatoes. So the actual combination is 2* 5C1
For the third course 3C1
Total no of ways = 3C1 * 5C1* 2 *3C1 = 90

ii) Only two courses can be picked. Possible choices - Starter-main, Starter-dessert, Main-dessert
Starter-main= 3C1* 5C1 *2 = 30
Starter-dessert= 3C1*3C1 = 9
Main-dessert= 5C1* 3C1 *2 =30
Total = 30 + 30 +9 =69

b) You have to find the different ways to divide not different arrangements. So, 14C5* 9C5 * 4C4 =252252.
The answer will be the same no matter which table you decide to chose first.

 

[Alice123]

5ai) For three courses a dish has to be picked from each course.
For the first course there are 3 options so 3C1
For the second course there are 5 options so 5C1. But each dish has two possible choices of being served with either fries or potatoes. So the actual combination is 2* 5C1
For the third course 3C1
Total no of ways = 3C1 * 5C1* 2 *3C1 = 90

ii) Only two courses can be picked. Possible choices - Starter-main, Starter-dessert, Main-dessert
Starter-main= 3C1* 5C1 *2 = 30
Starter-dessert= 3C1*3C1 = 9
Main-dessert= 5C1* 3C1 *2 =30
Total = 30 + 30 +9 =69

b) You have to find the different ways to divide not different arrangements. So, 14C5* 9C5 * 4C4 =252252.
The answer will be the same no matter which table you decide to chose first.

thanks a lot

 

[HubbaBubba]

Sum of coded values = -60
Σx = -60 + (24*36) = 804

Σ(x-36)^2 = 227.76
Expand LHS:
Σ(x^2 - 72x + 1296) = 227.76
Σx^2 - 72Σx + Σ1296 = 227.76
We have Σx = 804 and Σ1296 = (1296)(24) = 31104
Σx^2 - (804)(72) + 31104 = 227.76
Σx^2 = 27011.76

I understood the Σx part, but not the Σx^2 part :/ Why did you do that?

 

[Dug]

I understood the Σx part, but not the Σx^2 part :/ Why did you do that?

I expanded Σ(x-36)^2 it to pull out the term Σx^2. That is what we are supposed to find.

Consider this example:

(a+b)^2 = 4
a^2 + 2ab + b^2 = 4

If we are given 'ab' and 'b^2', we can easily find a^2 by putting the values into the equation. My solution is exactly the same. Did you get it now?

 

[Kumkum]

AOA wr wb
can someone pls help me with question 5(i)
http://papers.xtremepapers.com/CIE/...AS Level/Mathematics (9709)/9709_s04_qp_3.pdf

 

[Busy Buddy]

Assalamualikum
Can someone please help me with question 7(ii), 8(i) & 11(ii).
Thanks a bunch in advance.

 

[messi10]

Paper 3 Help needed
Paper: http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s10_qp_31.pdf

Question No. 10 - Part (iii)

Someone please help me with it. Please explain with basic concepts.. Paper 3 is killing me!! Please please help :'(