« previous next »
Pages: [1] 2   Go Down

Author Topic: Math  (Read 6661 times)

Offline Tutu_93

  • Newbie
  • *
  • Posts: 31
  • Reputation: 13
Math
« on: October 17, 2009, 01:18:15 pm »
I have a question in math sl
emm USe the method of completing the square to find the minimum value of y and and x at which it occurs

eg : y=x2 + 4x + 6

Waat do they mean ??

And i have texas Ti-84 silver edition .. how can i use it to graph and that stuff ??
Logged

Offline Tutu_93

  • Newbie
  • *
  • Posts: 31
  • Reputation: 13
Re: Math
« Reply #1 on: October 17, 2009, 01:24:46 pm »
Some 1 ??? :-\
Logged

Offline Ghost Of Highbury

  • O_o_O lala!
  • SF Farseer
  • *******
  • Posts: 4096
  • Reputation: 41428
  • Gender: Male
  • Namaskaram!
Re: Math
« Reply #2 on: October 17, 2009, 01:25:16 pm »
Quote from: Tutu_93 on October 17, 2009, 01:18:15 pm
I have a question in math sl
emm USe the method of completing the square to find the minimum value of y and and x at which it occurs

eg : y=x2 + 4x + 6

Waat do they mean ??

And i have texas Ti-84 silver edition .. how can i use it to graph and that stuff ??

(x+2)2 + 2

dy/dx of x2 + 4x + 6 = 2x+4

equate it to 0

2x = -4

x=-2

when x=-2

y = 2

thus the minimum point is (-2,2)
Logged
divine intervention!

Offline Tutu_93

  • Newbie
  • *
  • Posts: 31
  • Reputation: 13
Re: Math
« Reply #3 on: October 17, 2009, 01:28:36 pm »
Dint understand ..
Anywayz thnnx  ;D
Logged

Offline Ghost Of Highbury

  • O_o_O lala!
  • SF Farseer
  • *******
  • Posts: 4096
  • Reputation: 41428
  • Gender: Male
  • Namaskaram!
Re: Math
« Reply #4 on: October 17, 2009, 01:29:12 pm »
Quote from: Tutu_93 on October 17, 2009, 01:28:36 pm
Dint understand ..
Anywayz thnnx  ;D

refer to ur book!
Logged
divine intervention!

Offline Tutu_93

  • Newbie
  • *
  • Posts: 31
  • Reputation: 13
Re: Math
« Reply #5 on: October 17, 2009, 01:31:06 pm »
its infront of me ..
but we have this teacher who doesnt knw how to explaain so im really fed up :'(
Logged

Offline Ghost Of Highbury

  • O_o_O lala!
  • SF Farseer
  • *******
  • Posts: 4096
  • Reputation: 41428
  • Gender: Male
  • Namaskaram!
Re: Math
« Reply #6 on: October 17, 2009, 01:33:11 pm »
Quote from: Tutu_93 on October 17, 2009, 01:31:06 pm
its infront of me ..
but we have this teacher who doesnt knw how to explaain so im really fed up :'(


completeing the square is a very easy method...chk google.com to find a resource on that..

and the later part...is just differentiating it..and equating it to 0 to find the stationary point ....

Logged
divine intervention!

Offline astarmathsandphysics

  • SF Overlord
  • *********
  • Posts: 11271
  • Reputation: 65534
  • Gender: Male
  • Free the exam papers!
Re: Math
« Reply #7 on: October 17, 2009, 02:33:41 pm »
Completing the square is writing a quadratic in the form (x+a)^2 +b. In the example you gave both a and b equal 2. I will post a link when i get home
Logged

Offline Tutu_93

  • Newbie
  • *
  • Posts: 31
  • Reputation: 13
Re: Math
« Reply #8 on: October 17, 2009, 03:12:17 pm »
Okaay :D ..
Thnnx By the way
Logged

Offline slvri

  • SF Master
  • ******
  • Posts: 1773
  • Reputation: 1735
  • Gender: Male
Re: Math
« Reply #9 on: October 17, 2009, 04:14:21 pm »
Quote from: Tutu_93 on October 17, 2009, 01:18:15 pm
I have a question in math sl
emm USe the method of completing the square to find the minimum value of y and and x at which it occurs

eg : y=x2 + 4x + 6

Waat do they mean ??

And i have texas Ti-84 silver edition .. how can i use it to graph and that stuff ??
ok.........y=x2+4x+6
y=(x2+4x)+6
y=((x)2+2(x)(2)+(2)2)+6-(2)2
y=(x+2)2+6-4
y=(x+2)2+2
Now the minimum value will occur when (x+2)2=0(remember this as a rule)
(x+2)2=0
x+2=0
x=-2
and the corresponding minimum value of y is
y=(-2+2)2+2
y=2
hope this helped :)
Logged
i hate A level...........

Offline astarmathsandphysics

  • SF Overlord
  • *********
  • Posts: 11271
  • Reputation: 65534
  • Gender: Male
  • Free the exam papers!
Re: Math
« Reply #10 on: October 17, 2009, 05:02:35 pm »
Logged

Offline sameer210394

  • SF Citizen
  • ***
  • Posts: 190
  • Reputation: 219
  • Gender: Male
Re: Math
« Reply #11 on: October 17, 2009, 06:42:54 pm »
Quote from: Tutu_93 on October 17, 2009, 01:18:15 pm
I have a question in math sl
emm USe the method of completing the square to find the minimum value of y and and x at which it occurs

eg : y=x2 + 4x + 6

Waat do they mean ??

And i have texas Ti-84 silver edition .. how can i use it to graph and that stuff ??

one simplest method....

this equation is written in the form of Ax2 + Bx + C

in such cases to find the turning point. use the following equations...

x = -B/2A

then solve for
y(x).

done...

if you want the proving part, plz ask ..
Logged
Son, if you really want something in this life, you have to work for it. Now quiet! They're about to announce the lottery numbers

Offline IGSTUDENT

  • SF Citizen
  • ***
  • Posts: 192
  • Reputation: 811
Re: Math
« Reply #12 on: November 10, 2009, 03:47:21 pm »
I have some questions in mathematical induction.

1. let a1,a2,a3,...be a sequence defined by
    a1=1,an=3an-1; n?1

    Show that an=3^n-1 for all positive integers n.


 Prove the following statement.
    n
2. ? 1/(2i-1)(2i+1)=n/2n+1       for each positive integer n.
    1

3. Use mathematical induction to prove that (5^n)+(9^n)+2 is divisible by 4,for n?Z+.

Thanks.
Logged

Offline astarmathsandphysics

  • SF Overlord
  • *********
  • Posts: 11271
  • Reputation: 65534
  • Gender: Male
  • Free the exam papers!
Re: Math
« Reply #13 on: November 10, 2009, 09:58:30 pm »
. let a1,a2,a3,...be a sequence defined by
    a1=1,an=3an-1; n?1

    Show that an=3^n-1 for all positive integers n.


 Prove the following statement.
    n
2. ? 1/(2i-1)(2i+1)=n/2n+1       for each positive integer n.
    1

3. Use mathematical induction to prove that (5^n)+(9^n)+2 is divisible by 4,for n?Z+.

Thanks.
1. a_1=3*1-1=3^1 -1=2

SO p(1) is true. Suppose p(k) is true, prove p(k+1) trues
a_{n+1} =3(3^{k} -1) -1=3*3^k-3-1=3^{k+1} -4 Are you sure this question is right?

2.\sum_1^n 1/(2i-1)(2i+1) =1/2 \sum_1^n 1/(2i-1) -1/(2i+1)=1-1/(2n+1)=1/2(2n/(2n+1))=n/(2n+1)

3.p(1) 5+9+2=16 hence p(1) is true
suppoose p(k) is true then (5^k)+(9^k)+2 is divisible by 4
p(k+1)-p(k) (5^(k+1))+(9^(k+1))+2-(5^k)-(9^n)-2  =5^k(5-1) +9^k(9-1)=4*5^k +8*9^k which is divisible by 4
« Last Edit: November 10, 2009, 10:12:13 pm by astarmathsandphysics »
Logged

Offline falafail

  • SF Master
  • ******
  • Posts: 1328
  • Reputation: 1486
  • Gender: Female
  • ab3'a 7asheesh
Re: Math
« Reply #14 on: November 10, 2009, 10:21:56 pm »
Quote from: Tutu_93 on October 17, 2009, 01:18:15 pm
I have a question in math sl
emm USe the method of completing the square to find the minimum value of y and and x at which it occurs

eg : y=x2 + 4x + 6

Waat do they mean ??

And i have texas Ti-84 silver edition .. how can i use it to graph and that stuff ??

y = x2 + 4x + 6
y = x2 + 4x + 22 - 22 + 6
y = (x + 2)2 - 4 + 6
y = (x + 2)2 + 2
the least value of y will be when (x + 2)2 = 0, so x = -2
substitute for y.

so when you're asked to "complete the square" basically this is what you do:
x2 + bx + c
x2 + bx + (b/2)2 - (b/2)2 + c
(x + b/2)2 - (b/2)2 + c
;D
« Last Edit: November 10, 2009, 10:24:44 pm by falafail »
Logged
Pages: [1] 2   Go Up
« previous next »