∣∣ ∣∣x+42x2x2xx+42x2x2xx+4∣∣ ∣∣=(5x+4)(4−x)2.
∣∣ ∣∣y+kyyyy+kyyyy+k∣∣ ∣∣=k2(3y+k)
LHS=∣∣ ∣∣x+42x2x2xx+42x2x2xx+4∣∣ ∣∣=∣∣ ∣∣5x+42x2x5x+4x+42x5x+42xx+4∣∣ ∣∣ (using C1→C1+C2+C3)
=(5x+4)∣∣ ∣∣12x2x1x+42x12xx+4∣∣ ∣∣ [take out (5x+4)common from C1].
=(5x+4)∣∣
∣∣12x2x0−x+4000−x+4∣∣
∣∣
Expanding along C1, we get
=(5x+4)[1(4−x)(4−x)]=(5x+4)(4−x2)=RHS
LHS=∣∣ ∣∣y+kyyyy+kyyyy+k∣∣ ∣∣=k2(3y+k)=∣∣ ∣∣3y+kyy3y+ky+ky3y+kyy+k∣∣ ∣∣ (using C1→C1+C2+C3)
=(3y+k)∣∣ ∣∣1yy1y+ky1yy+k∣∣ ∣∣ [take out (3y+k) common from C1]
=3y+k∣∣
∣∣1yy0k000k∣∣
∣∣ (using R2→R2−R1 and R3→R3−R1)
Expanding along C3. we get
=(3y+k)(1×k.k)=k2(3y+k)=RHS.