(ab - ad) / (abd) = a(b - d) / (abd) = (b - d) / (bd ) = 1/d - 1/b
xyz /(z * ( x-y)) = xy / (x-y)
Ответ:
Объяснение:
202*198 = 39996 = 40000 - 4 = 200^2 - 2^2
1.
(x-4)²-(x+9)²=195
x²-8x+16-(x²+18x+81)=195
x²-8x+16-x²-18x-81=195
-26x=195-16+81
-26x=260
x=-10
Ответ x=-10.
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2.
x+7x²-y-7y²=(x-y)+7(x²-y²)=(x-y)+7(x-y)(x+y)=(x-y)(1+7x+7y)
Ответ: (x-y)(7x+7y+1).