math help:inequalities?

2008-03-08 4:54 pm
does anyone know a good website for tutoring where you can chat with a tutor?
and also can someone show me the easiest and quickest way to solve these problems?
7x+4=3x+16

and

1/4(6n-3)=4n+1
更新1:

what about: 3n+9=7n-15?

更新2:

and: 29x+3)=8?

回答 (4)

2008-03-08 5:13 pm
✔ 最佳答案
In this type of problems, you want to organize and keep what you want to find on one side of the equal side and on this problem we want to find x. to move a number from one side to the other we do the opposite to cancel it out like +4 :
7x +4= 3x +16
-4 -4
7x=3x+16-4 is
7x=3x+12
-3 -3x so
7x-3x=3x-3x+12
4x=12
now the opposite of multiplication is division so that is our next step to cancel that 4 and leave the x by itself. just remember if you do it to one side, you have to do it to the other:
4x+12
/4 /4
4/4=1 so
1x=x then
x=12/4=3
2008-03-09 1:36 am
well its really simple what you need to understand is the unknown and constant, unknown are letters for example (X, Y, N etc.) and the constant are the numbers. (1,2,3 etc)

well the equal to sign (=) is like a bridge both the constant and unknowns has to cross.

remember when doing inequalities you should separate the
unknowns and the constants.

well lets try it:
7x+4=3x+16

1st step: separate the unknowns and the constants

i will put all the unknowns in the left hand side and the constants on the right hand side

7x - 3x=16 - 4

VERY IMPORTANT: when both the constant and unknown crosses the ( = ) bridge, their sign either ( - or + ) changes.

what happen is that after +3x and +4 crosses the bridge it becomes -3x and -4. you should note that any number is positive (+) number

2nd step: so then it become quite simple you add the unknown and the constant in other word you simplify the equation.

7x - 3x=16 - 4
4x=12

3rd step: you should always simplify the equation in a way that the unknown stand alone ( i mean that our goal is to know the value of x) so we need to convert 4x into x.

the number which appear before the unknown is called a coefficient. example (the coefficient of 4x is 4, the coefficient of 3x is 3, the coefficient of 5x is 5, the coefficient of x is 1,)

4x=12
now we should eliminate the coefficient 4x in order to find the value of x.

the only way to eliminate coefficients is use division.

NOTE THAT when you divide an unknown you should also divide the constant which is on the other side of the (=) bridge

4x=12
in order to get x, by what factor should i divide 4x?
by 4, why?

because 4x divide by 4 makes x.
if i divide my unknown by 4 i should also divide my constant by 4.

so.........

x=3. TADA...


now 1/4(6n-3)=4n+1

when there is a number before a bracket that mean the number multiplies with the constant and unknown inside the bracket.

(6n-3) is inside the bracket, 1/4 is before the bracket.

1st step. simply the left hand side of the equation by multipling 1/4 and (6n-3)
which gives 1/4 x 6n= 6/4n
1/4 x -3= -3/4

so the left hand side of the equation becomes:

6/4n - 3/4=4n+1

by applying all the steps i teach you

6/4n - 3/4=4n+1
6/4n-4n=1+3
-5/2n=4

now you divide by -5/2

n= -8/5 voila....


ONE MORE THING I FORGET TO MENTION WHEN YOU DIVIDE A NEGATIVE UNKNOWN THE CONSTANT ALSO MUST BE DIVIDE BY THE NEGATIVE UNKNOWN.

for example:

-3x =3
x= -1

-1/2x=4
x= -8

and

-5y= -25
y= 5


well i this website
http://mathworld.wolfram.com/WolfPrize.html

i used when i was in high school
2008-03-09 1:15 am
1)
7x + 4 = 3x + 16
7x - 3x = -4 + 16
4x = 12
x = 12/4
x = 3

2)
1/4 (6n - 3) = 4n + 1
(6n - 3)/4 = 4n + 1
6n - 3 = 16n + 4
6n - 16n = 3 + 4
-10n = 7
n = 7/-10 (-0.7)

3)
3n + 9 = 7n - 15
3n - 7n = -9 - 15
-4n = -24
n = -24/-4
n = 24/4
n = 6
2008-03-09 1:03 am
Don't use the guy who advertises here under various pseudonyms. Unless you speak Hindi better than he speaks English.
-------------------
You need to combine the x terms and move remaining terms to the other side of the equals sign.

7x + 4 = 3x + 16

Subtract 3x from both sides of equation:
7x - 3x + 4 = 3x - 3x + 16
4x + 4 = 16

Subtract 4 from both sides:
4x + 4 - 4 = 16 - 4
4x = 12

Divide both sides by the coefficient of x, which is 4:
4x/4 = 12/4
x = 3
------------------
(1/4)(6n - 3) = 4n + 1

Multiply both sides of equation by 4
4(1/4)(6n - 3) = (4n + 1)4
6n - 3 = 16n + 4

Subtract 6n from both sides
6n - 6n - 3 = 16n - 6n + 4
-3 = 10n + 4

Subtract 4 from both sides
-3 -4 = 10n + 4 - 4
-7 = 10n

Divide both sides by coefficient of n, i.e., 10
-7/10 = 10n/10
-7/10 = n


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