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Pair Of Linear Equations In Two Variables

Question
CBSEENMA10006748

Solve the following pairs of equations by reducing them to a pair of linear equations :

4 over straight x plus 3 straight y equals 14
3 over straight x minus 4 straight y equals 23




Solution
Let space space space space space space space 1 over straight x equals straight a

Thus, the given equations become
4a + 3y = 14    ...(i)
3a - 4y = 23    ...(ii)
For making the coefficient of ‘y’ in (i) and (ii), we multiply (i) by 4 and (ii) by 3 and then adding, we get

space space space 16 straight a plus 12 straight y equals 56
bottom enclose space space space 9 straight a minus 12 straight y space equals 69 space space space space space end enclose
25 straight a space space space space space space space space space space equals space 125
rightwards double arrow space space space space space space straight a space equals space 125 over 25
rightwards double arrow space space space space space space straight a equals 5
Putting the value of ‘a’ in (i), we get
4a + 3y = 14
rightwards double arrow space space space space space space space 4 left parenthesis 5 right parenthesis space plus space 3 straight y space equals space 14
rightwards double arrow space space space space space space space space 20 straight y space plus space 3 straight y space equals space 14
rightwards double arrow space space space space space space space space 3 straight y space equals space minus 6
rightwards double arrow space space space space space space space space space straight y space equals space minus 2
Now space space space space space space space straight a space equals space 5
rightwards double arrow space space space space space space space space space space space 1 over straight x equals 5
rightwards double arrow space space space space space space space space space space space space straight x space equals 1 fifth

Hence,  space space space space space space space space space space space space space space straight x equals 1 fifth space and space straight y space equals negative 2, is the solution of the given equation.