Question

выполни действие:
1)(10-k)(k+10)
2)(4/9x-y)(y+4/9x)
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Answer 1

Ответ:

$1)(10-k)(10+k)=10^2-k^2=100-k^2$

$2)({4\over9}x-y)(y+{4\over9}x)=({4\over9}x-y)({4\over9}x+y)=({4\over9}x)^2-y^2={16\over81}x^2-y^2$