Q9 of 37 Page 1

Find the value(s) of k for which the pair of linear equations kx + y = k2 and x + ky = 1 have infinitely many solutions.

We have the linear equations,

kx + y = k2 …(i)


x + ky = 1 …(ii)


We can rewrite equations (i) & (ii) as,


kx + y – k2 = 0 …(iii)


x + ky – 1 = 0 …(iv)


Comparing equation (iii) from a1x + b1y + c1 = 0, we get


a1 = k, b1 = 1 and c1 = -k2


Comparing equation (iv) from a2x + b2y + c2 = 0, we get


a2 = 1, b2 = k and c2 = -1


Also, given that kx + y = k2and x + ky = 1 have infinitely many solutions. So, we can write as



Putting in values,



Solving ,


k2 = 1


k = √1


k = 1 …(v)


Also solving ,


k3 = 1


Or k3 = 13


k = 1 …(vi)


Hence, k = 1 because it satisfies both equations (v) and (vi).


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