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[Corn Bird]

thanks fellas ^ . but on second thought, the 5 x 5 system

x5+x3=14
x4-x2=1
2x2-x1=1
x2+x3=10
x1+x2+x3+x4+x5=30

can be solved by substitution. the first four equations give

x1=2x2-1
x4=x2+1
x3=10-x2
x5=14-x3=14-(10-x2)=4+x2

and substitute into the fifth to get

(2x2-1)+x2+(10-x2)+(x2+1)+(4+x2)=30

4x2=16
x2=4


then put back x2 into the above four expressions for x1, x3, x4, x5 to get the answer

x1=7 x2=4 x3=6 x4=5 x5=8




no need for row reduction here...

[Ronaldo95163]

^ I never did row reduction in Matrices before

[Ronaldo95163]

stev where you does find them questions??? I ketchin my tail to find questions on the web

[Corn Bird]

^ I never did row reduction in Matrices before

videos below give examples of row reduction. the first video explains the process; the second video is probably a more standard example of a unique solution

[stev]

stev where you does find them questions??? I ketchin my tail to find questions on the web

hard to say...random websites that comes up on google. lol.

eg: http://library.thinkquest.org/J002235/hard.html


here's a nice one on there:

One day, a person went to a horse racing area. Instead of counting the number of humans an horses, he conuted 74 heads and 196 legs. How many humans and horses were there?

[stev]

btw...those are the exact videos i looked at wen i was doing matrices. it helped a lot.

[Corn Bird]

One day, a person went to a horse racing area. Instead of counting the number of humans an horses, he conuted 74 heads and 196 legs. How many humans and horses were there?

x+y=74
2x+4y=196

assuming standard numbers of legs and head per man/horse.

btw...those are the exact videos i looked at wen i was doing matrices. it helped a lot.

these videos were recommended by the teacher?

[Ronaldo95163]

Nice

What level of math is that BTW Corn Bird....the row reduction

BTW here's another question

Prove the following

sinx/1+cosx + 1+cosx/sinx is equivalent to 2cosecx

The original question used theta instead of x BTW

[Corn Bird]

What level of math is that BTW Corn Bird....the row reduction

it's done in cape pure math unit 2

Prove the following

sinx/ (1+cosx ) +( 1+cosx)/sinx is equivalent to 2cosecx

brackets are important..

sinx/(1+cosx) + (1+cosx)/sinx

=(sin(x)^2 + (1+cos(x))^2)/((1 + cos x)(sin x))

= (2 + 2 cos x)/((1 + cos x)(sin x))

=2/sin x

=2 cosec x

[Ronaldo95163]

Sorry about the brackets....that's how I saw the question

Try this one

[mamoo_pagal]

don't mean to stray off........but got to appreciate this

[Ronaldo95163]

Last identity givin me rel stress dan.....idk if I doing something wrong and I not seeing it but I just aint gettin the answer >.<

[Corn Bird]

Try this one

given identity does not seem correct. this is what i get

try substituting x=45 degrees. then left side of your identity gives -1.

[Ronaldo95163]

Yea I think there was an error in the question

#8 is the question

[stev]

One day, a person went to a horse racing area. Instead of counting the number of humans an horses, he conuted 74 heads and 196 legs. How many humans and horses were there?

x+y=74
2x+4y=196

assuming standard numbers of legs and head per man/horse.

btw...those are the exact videos i looked at wen i was doing matrices. it helped a lot.

these videos were recommended by the teacher?

nope...teacher jus recommended some crazy text book. I had to teach myself. lol

[turbo_boy411]

hey can anyone help me with these questions on the following post.

the link is below, thanks

viewtopic.php?f=4&t=428442

[stev]

[Corn Bird]

hey can anyone help me with these questions on the following post.

the link is below, thanks

viewtopic.php?f=4&t=428442

the point about homework is that you get practice. if you don't lift the weight yourself you will never develop strength

1. formulate the question correctly. given problem can be rewritten as:

if n is a prime and n+1 is a perfect square then n=3.

now use the definitions of 'prime' and 'perfect square' to get n+1=a^2. then write as
n=a^2-1. factorize the right side and use the fact that n is prime


2. this is a more standard problem than the first -- that is, it is a typical induction problem, only thing different is that it starts at n=2. calculate the first few cases using the given formula, you will get f1=1, f2=1, f3=2, f4=3. use this to prove the start case which is

f1+f2=f4 -1

now do the induction step, assume statement is true for n=k that is

f1+f2+...+fk=f_{k+2} -1

using this, show that the n=k+1 case is true

f1+......+f_{k+1}
=(f1+.......+f_k) + f_{k+1}
=
=
=f_{(k+1)+2}-1

[turbo_boy411]

hey thanks cornbird for the help, its just i couldnt figure out these two but i will practice more. thanks again

[Ronaldo95163]

I got someone who proved the identity @CornBird.....when I get time ima post the solution

[Corn Bird]

I got someone who proved the identity @CornBird.....when I get time ima post the solution

i checked the identity with some software. according to the maple command 'testeq', the identity as given is false. my answer above of 1-sec(x)^2 seems to be correct

[Ronaldo95163]

oooooooh

BTW maple looks sweet! ^_^

[Around]

lol

[Corn Bird]

dr gracen, it isn't too hard to check if an identity is true or false. these trig identities usually hold for all values of x. notice that this one does not hold for when x=Pi/4= 45 degrees. for x=Pi/4, we have sec(x)^2=2. but the lhs is equal to -1.

Untitled (2).jpg (11.6 KiB) Viewed 1957 times

this gives an indication that the identity is false.

on a related note, identities need not hold for all values of x. a standard example is the infinite g.p

1/(1-x)=1+x+x^2+x^3+....

this identity only holds for -1< x <1.

some identities hold for intervals, some hold for all x. you were talking about taylor series previously. this taylor series holds for all x

e^x=1 + x + x^2/2! + x^3/3! + ...

[Ronaldo95163]

Thanks for the advice

[Ronaldo95163]

[gencon]

I hate algebra!! bleh!!

[Rooki3]

the virginity is strong in here

[Ronaldo95163]

I hate algebra!! bleh!!

Algebra rel awesome. Why you hate it?

[gencon]

I hate algebra!! bleh!!

Algebra rel awesome. Why you hate it?

anything beyond cxc maths was and still is an epic fail for me.