396.° Спростіть вираз: 1) 7x (x - 4) - x (6 - x); 2) 5ab (4a +3b)-10a² (2b -4); 207 3) xy (2x-11y)-x(xy+14y²); 4) 5c³ (4c-3) - 2c² (8c² -12).

7x(x - 4) - x(6 - x) = 7x {}^{2} - 28x - 6x + {x}^{2} = 8 {x}^{2} - 34x

5ab(4a + 3b) - 10 {a}^{2} (2b - 4) = 20 {a}^{2} b + 15ab {}^{2} - 20 {a}^{2} b + 40 {a}^{2} = 15ab {}^{2} + 40a {}^{2}

xy(2x - 11y) - x(xy + 14 {y}^{2} ) = 2 {x}^{2} y - 11x {y}^{2} - {x}^{2} y - 14x {y}^{2} = {x}^{2} y - 25x {y}^{2}

5c {}^{3} (4c - 3) - 2 {c}^{2} (8c {}^{2} - 12) = 20 {c}^{4} - 15c {}^{3} - 16 {c}^{4} + 24 {c}^{2} = 4 {c}^{4} - 15c {}^{3} + 24 {c}^{2}