П.31 Решите уравнения: 1) (7 cdot (x - 4) - 7 = 8 cdot (x - 4)); 2) (6 cdot (x - 7) + 13x = 7 cdot (2x - 6) + 27); 3) ((1{,}3y - 5{,}9) cdot (-3{,}5) = 6{,}8y - 11{,}13); 4) (1{,}2 cdot (z - 2{,}1) = 1{,}3 cdot (z - 1{,}6) - 0{,}52).

Решение: 1) (7(x - 4) - 7 = 8(x - 4)) (7x - 28 - 7 = 8x - 32) (7x - 35 = 8x - 32) (8x - 7x = -35 + 32) (x = -3) Ответ: (x = -3) 2) (6(x - 7) + 13x = 7(2x - 6) + 27) (6x - 42 + 13x = 14x - 42 + 27) (19x - 42 = 14x - 15) (19x - 14x = -15 + 42) (5x = 27) (x = rac{27}{5}) (x = 5{,}4) Ответ: (x = 5{,}4) 3) ((1{,}3y - 5{,}9) cdot (-3{,}5) = 6{,}8y - 11{,}13) (-4{,}55y + 20{,}65 = 6{,}8y - 11{,}13) (6{,}8y + 4{,}55y = 20{,}65 + 11{,}13) (11{,}35y = 31{,}78) (y = rac{31{,}78}{11{,}35}) (y = 2{,}8) Ответ: (y = 2{,}8) 4) (1{,}2(z - 2{,}1) = 1{,}3(z - 1{,}6) - 0{,}52) (1{,}2z - 2{,}52 = 1{,}3z - 2{,}08 - 0{,}52) (1{,}2z - 2{,}52 = 1{,}3z - 2{,}6) (1{,}3z - 1{,}2z = -2{,}52 + 2{,}6) (0{,}1z = 0{,}08) (z = rac{0{,}08}{0{,}1}) (z = 0{,}8) Ответ: (z = 0{,}8)