Question

factorise 9x²+49y²+z²-42xy+14yz-6zx and hence find its value , when x=2,y=1and z=-1​

Answer 1

Answer:

9x^2+49y^2+z^2-42xy+14yz-6zx=(3x+7y+z)^2 =(3×2+7×1-1)^2 =(6+7-1)^2 =(12)^2

=144