Question 81324
QUESTION:


4x-3y=33
x=-4y-25



ANSWER:


4x-3y=33------------------(1)


The second equation,x=-4y-25 can be written as,




x=-4y-25


==> x + 4y = -25 ----------------(2)



Multiply equation(2) with 4 so that coefficient of becoma same in both the equations(You can make coeffeicient of y same and can follow the following procedure.)



==> 4(x + 4y ) = 4* -25



==> 4x  + 16y = -100 ----------------------(3)



Now we have,



4x - 3y = 33------------------(1)


4x  + 16y = -100 ----------------------(3)




Subtract (3) from (1)



==> 4x - 3y - ( 4x + 16y ) = 33 - (-100)



==> 4x - 3y - 4x - 16y  = 33 + 100



==> -19y = 133



Divide both sides by -19



==> -19y/-19 = 133/-19



==> y = -7



Now substitute this value in any of the given equations.....


Lets take (1)



==> 4x - 3 (-7) =33



==> 4x + 21 = 33



Subtract 21 from both sides....



4x + 21 -21 = 33 - 21



==> 4x = 12



Divide both sides by 4



==> 4x/4 = 12/4



==> x = 3



so the solution is,


x = 3 and y = -7




Hope you found this method useful.



Regards.




Praseena.