Question 45818
4X-Y+3Z
4X-Y-3Z
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16X~2-4XY+12XZ
.....-4XY.....+Y~2-3YZ
.........-12XZ....+3YZ-9Z~2
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16X~2-8XY......+Y~2...-9Z~2

the final answer is 16x~2-8xy+y~2-9z~2