Question

Find the value of k for which a pair of linear equations x+y=3,x-y=k which has unique solution

Answer 1

Use the formula: of cross multiplication

2/k-1=3/k+2=-7/-3k

2×(k+2)=3×(k-1)

2k+4=3k-3

2k-3k=-3-4

-k=-7

k=7