MULTIPLICATION PRINCIPLE

[mnkrebs]

I have two questions- how do I solve 11x=-99 using the multiplcation principle.

How do I solve 7+3x<13 using the addition and multiplication principles?

 

[Denis]

Please post the "definition" of both principles; the one you intend to use.

 

[mnkrebs]

I guess I dont know what you mean by "definition"- I am supposed to solve the first problem-11x=-99 by using the multiplication principle, and the second problem -7+3x<13 by using the addition and multiplication principles together.

 

[CodePoet]

Well, if you are asked the question "What is the multiplication principle?" what would you answer?

 

[mnkrebs]

I would answer you multiply, but that doesn't tell me how to solve the problems in question.

 

[wjm11]

I have two questions- how do I solve 11x=-99 using the multiplcation principle.

How do I solve 7+3x<13 using the addition and multiplication principles?

See the examples here:

http://library.thinkquest.org/20991/alg2/eq.html

Also, with inequalities, if you multiply or divide by a negative number, the direction of the inequality symbol "flips".

Hope that helps.

 

[mnkrebs]

Not much- so for 11x=-99, am I multiplying -99 times the fraction one eleventh?

 

[CodePoet]

Yes, it should reduce down to a usable answer.

 

[mnkrebs]

I came up with -9. Is that right?

 

[wjm11]

for 11x=-99, am I multiplying -99 times the fraction one eleventh?

Yes.

The big picture is simply this: Whatever you do to one side of the equation, you must do to the other side as well.

In this problem, we see that x is being multiplied by 11. To get rid of that 11, we do the “reverse” of multiply – we divide by 11. (Note that dividing by 11 and multiplying by 1/11 are equivalent – just two different ways of doing/saying the same thing.)

11x=-99
(11x)/11 = (-99)/11
x = -9

Good job!

 

[mnkrebs]

Thank you