Homework Help: Algebra

Posted by JERSEYGIRL on Sunday, December 4, 2011 at 8:49pm.

40 =15
x x - 20 This is a three part question>> first find the lcd method of solving this equations, and the second ones about cross-multiplying method to solve this equations ,The next question asked would the cross- multiplying method work for all rational equations?? Explain.

Algebra - Reiny, Sunday, December 4, 2011 at 9:02pm
I am guessing you are trying to type the equation

40/x = 15/(x-20)

The LCD is x(x-20_
so
40/x (x(x-20)) = 15/(x-20) (x(x-20))
40(x-20) = 15x
40x - 800 = 15x
25x = 800
x = 32

cross-multplying gets you directly to
40(x-20) = 15x
etc

Cross-multiplying only works if your equation contains a single term on the left and a single term on the right,
that is,
you have to add/subract the terms first if you have more than one.
In that case I simply multiply each term by the LCD, to get rid of my fractions.
Algebra - JERSEYGIRL, Sunday, December 4, 2011 at 9:42pm
(1)40 =15 (2) x - 20 (2 DIFFERENT EQUATIONS)????? help please!!!!

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