Ответ:
1. х²-ху+ху-у²=х²-у²
2. n²+nm-nm-m²=n²-m²
3. k²+2k-2k-4=k²-4
4. 9+3c-3c-c²=9-c²
AB=X
BC=3X
S=AB*BC
S=x*3x
16=4x
x=4см
Ответ:4см
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x2 - 8x + 15 = 0D = b2 - 4acD = 64 - 60 = 4 = 2^2