Math Is Fun Forum

Thanks for the very fruitful discussion; I would like to put the following notes:
 
  1.  The lim of f(x) as x approaches n is equal to f(n) if f(n) is defined , this statement should be changed to : if n is in the domain of f(x).

2. [x] = - [-x] if x is integer only

3. very interested to be introduced to the idea of flooring and ceiling , since I  never see it in the American books

Hi
I strongly believe that doing "good" in maths is a matter of love !!
if u love ALGEBRA u'll do "good"
I believe also that loving maths is not related to the material itself!!, in someway its related to the atmospher surrounding it , the teacher is the first and most important factor

To solve ur problem , take these advises:

1. Don't tel urself that u have a bad relation with algebra and u will never reach the right answer...tell urself always and laudly that ur good and algebra is a nice friend

2. Start from the zero level and memorize all the definitions and rules in ur way , u can use this site to start with 

3. Always use ur pencile and papers in solving a problem , don't rely on ur eyes alone.

4. whenever u have a wrong answer , go back and solve a gain after knowing the right answer.

1000a + b = 3ab
1000a - 3ab = -b
a( 1000 - 3b) = -b
a ( 3b - 1000) = b

a = b / ( 3b - 1000)

This is a question found in a " pre calculus " book , the authers put 80 m and 60 m as the answers , i could reach one equation in two variables , but never come to a second equation .
Now , if we know that the answer should be 60 m and 80 m , can we work back to find any new equation !!
thanks Dross
thanks mathsyperson

Sorry to say that HOOYOO solution is wrong ,
solving the two equations given by HOOYOO will give x= 1112.76, y = 1767.24 but
if we check by multiplying x and y by 1.2 it will not sum up to 3000.

this is my solution :

Let x the cost of table and y the cost of chair

he sold the table and the chair at 3000 and made 20% profit
(x + y)*1.2 = 3000
x + y = 2500
2500 is the cost of both table and chair
if he sells the chair at cost and the table at 1800 , he would make 12 %
y + 1800 = (2500 * 1.12)
y + 1800 = 2800
y = 1000
1000 is the cost of chair
x = 2500 - 1000 = 1500
1500 is the cost of table

hi ,
for a line passing through (x1,y1) and (x2,y2) , use this equation :
m (slope) = (y2-y1)/(x2-x1)
y-y1 = m(x-x1)
in our case :
m= 24-2 / 12-1 = 22/11 = 2
y - 2 = 2 ( x- 1)
y - 2 = 2x-2
y = 2x

For the circle :
The equation used is the standard equation that has the form

(x - h)² + (y - k)² = r2
where h and k are the x- and y-coordinates of the center of the circle and r is the radius.
( x-3)[sup]2[/sup] + ( y-3)[sup]2[/sup] = 81