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(a + 5)^2 = a^2 + 10a + 25  ;   б) (3у - х)^2 = 9y^2 - 6xy + x^2 ;       в) (2b - 1) * (2b + 1) = 4b^2 - 1    ;   г) (4a + 3b)(3b - 4a) = - (4a + 3b)(4a - 3b) = - (16a^2 - 9b^2) = 9b^2 - 16a^2 a) b^2 - 16 = (b + 4)(b - 4)  ; б) 4a^2 - 12a + 9 = (2a - 3)(2a + 3)  ; в) 27x^3 + 125 = 3^3x^3 + 5^3 = (3x + 5)(9x^2 - 15x + 25) (a - 3)^2 - 3a(a - 2) = a^2 - 6a + 9 - 3a^2 + 4 = - 2a^2 - 6a + 13 a) (x - 3)^2 - x(x + 2.7) = 9    ;   x^2 - 6x + 9 - x^2 - 2.7x = 9    ; - 8.7x = 9 - 9      - 8.7x = 0    ; x = 0 б) 9y^2 - 25 = 0    ;   3^2y^2 - 5^2 = 0      ;     (3y + 5)(3y - 5) = 0    ;     (3y + 5) = 0       3y = - 5    ;     y' = - 5/3  ;     (3y - 5) = 0  ;   3y = 5  ;   y" = 5/3 a) (x^2 + 1)(x + 1)(x - 1) = (x^2 + 1)(x^2 - 1) = x^4 - 1 б) (3a^2 - 6b^2)(a^2 + 2b^2) = 3(a^2 - 2b^2)(a^2 + 2b^2) = 3(a^4 - 4b^4) =  3a^4 - 12b^4 а) 49a^2b^4 - 100c^4 = (7ab2 + 10c^2)(7ab2 - 10c^2) б) (x + 3)^2 - (x - 3)^2 = ((x + 3) + (x - + 3) - (x - 3)) = 2x (2x+6) b) (x + 5)^3  - (x - 5)^3 = a^3 - b^3 = (a + b)(a^2 - ab + b^2) = ((x + 5) + (x - + 5)^2 - (x + 5)(x - 5) + (x -5)^2) =(x + 5 + x - 5)(x^2 + 10x + 25 - x^2 - 25 +x^2 - 10x + 25) = (2x) (x^2 + 25)