find x²+y²+z²+2xy-2yz-2zx,if x=4,y=-5,z=7
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Step-by-step explanation:
x=4,y=-5,z=7
x²+y²+z²+2xy-2yz-2zx
=4² + 5² + 7² + 2 * 4 * 5 - 2 * 5 * 7 - 2 * 7 * 4
= 16 + 25 + 49 + 40 - 70 - 56
=4
or
x²+y²+z²+2xy-2yz-2zx= (X+y-z) ²
=(4+5-7) ²
=(2) ²
=4
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