For which values of a and b does the following pair of linear equations have an infinite number of solutions?

2x + 3y = 7


(a – b)x + (a + b)y = 3a + b - 2


(i) 2x + 3y - 7 =0

(a - b)x + (a + b)y - (3a + b - 2) = 0





For infinitely many solutions,




6a + 2b - 4 = 7a – 7b


a – 9b = -4.............. (i)



2a + 2b = 3a – 3b


a – 5b = 0...............(ii)


Subtracting (i) from (ii), we obtain


4b = 4


b = 1


Substituting this in equation (ii), we obtain


a - 5 × 1 = 0


a = 5


Hence, a = 5 and b = 1 are the values for which the given equations give infinitely many solutions.


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