1. а) (a-3)^2 : (a-3) = a-3= 4,7 - 3 = 1,7;
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б) 6x(3x-y) :((3x-y)(3x+y)) = 6x :(3x+y)= (6*1) : (3*4 +3)= =6: 15 = 0,4.
2. а)(5x -y)(5x+y) = 25 x^2 - y^2
б) (a+4)^2 - 2a(a-3) =a^2 + 8a +16 - 2a^2 + 6a =
= - a^2 +14a +16.
3. 5a - 5b + c(a - b) = 5(a - b) + c(a - b)=(a-b)(5 +c);
a^3 - a^2 - 4a + 4 = (a^2 - a^2) - ( 4a - 4) = a^2(a -1) - 4(a-1) = (a-1( a^2 -1) = (a-1)(a+2)(a-2).