If x-y=4,y-z=3,x=7 then find out ,x square+y square+z square-xy-yz-zx=

1.	If x-y=4,y-z=3,x=7 then find out ,x square+y square+z square-xy-yz-zx=?
Answer» If x=7 than y=3,z=14×4+3×3+1×1-4×3-3×1-1×4=16+9+1-12-3-4=26-19=7.

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