kirillsych 1)9a (5a-4b^2) = 9a×5a - 9a×4b^2 = 40a^2 - 36ab^2
2)-n (p+2n-1n) = -np - 2n^2 - (-n^2) = - np - 2n^2 +n^2
3)0,7 (3p - 2q) + 4q = 2,1p - 1,4q + 4q = 2,1p + 2,6q
4)2x^2(4 - 9x) - 3x (x^2 - 4) = 8x^2 - 18x^3 - 3x^3 + 12x = 8x^2 - 21x^3÷ + 12x