In questions liken"If x/y=7/0, find (2x-3y)/(5x-4y)." can't I just subtitute the values of x & y in the ques. or is it necessary to use the formula?If yes, then please explain me how to do it briefly.

Asked by savi1405 | 10th Jun, 2016, 10:29: PM

Expert Answer:

begin mathsize 12px style I f space x over y equals 7 over 10 comma space i t space d o e s space N O T space m e a n space x equals 7 comma space a n d space y equals 10.
I t space s i m p l y space m e a n s space t h e space r a t i o space o f space x space t o space y space i s space a l w a y s space 7 colon 10.
S o space w e space c a n t space a l w a y s space d i r e c t l y space s u b s t i t u t e. space
T h e space b e s t space w a y space i s space t o space t a k e space apostrophe x apostrophe space a s space 7 a space a n d space y space a s space 10 space a.
T h e n space d o space t h e space s i m p l i f i c a t i o n space o f space t h e space e x p r e s s i o n. space
P l e a s e space n o t e space t h a t comma space i n space t h i s space e x p r e s s i o n space fraction numerator 2 x minus 3 y over denominator 5 x minus 4 y end fraction comma
i t space w o n apostrophe t space m a k e space a n y space d i f f e r e n c e space w h e t h e r space y o u space t a k e space x space a n d space y space a s space 7 space a n d space 10
o r space 7 a space a n d space 10 a.
B u t comma space i n space g e n e r a l space t h a t space w o n apostrophe t space b e space t h e space c a s e comma space
S o space i t space i s space a d v i s a b l e space t o space e x p r e s s space apostrophe x apostrophe space a n d space apostrophe y apostrophe space a s space 7 a space a n d space 10 a.
T h e n comma space y o u space c a n space s u b s t i t u t e space i n space t h e space e x p r e s s i o n space a n d space s i m p l i f y space t o space g e t space t h e space v a l u e.
H o p e space t h a t space c l e a r s space y o u r space d o u b t. space space end style

Answered by satyajit samal | 13th Jun, 2016, 09:15: AM