Step-by-step explanation:

1. (7xy-5z²)²

(7xy-5z²)(7xy-5z²)=0

49x²y²-35xy z²-35xy z²+25z⁴=0

49x²y²-70xy z²+25z⁴=0

2. (3x²+5y⁴)²=0

(3x²+5y⁴)(3x²+5y⁴)=0

9x⁴+15x²y⁴+15x²y⁴+25y8=0

9x⁴+30x²y⁴+25y8=0

3.(x+2y+3w-z)(x+2y-3w+z)=0

x²+2xy-3wx+xz+2xy+4y²-6wy+2yz+3wx+6wy-9w²+3wz-xz-2yz+3wz-z²=0

x²+2xy-3wx+xz+4y²-6wy+2yz-9w²+3wz-z²

+2xy+3wx-xz. +6wy-2yz. +3wz

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x²+4xy +4y² -9w²+6wz-z²=0

final answer:x²+4xy+4y²-9w²+6wz-z²=0