Вправа 880 алгебра Бевз гдз 7 клас
№ 880
а) (x2 – 2)2 – х4 = 0
(х2 – 2)2 – (х2)2 = 0
(х2 – 2 + х2)(х2 – 2 – х2) = 0
–2 • (2х2 – 2) = 0
–4(х2 – 1) = 0
–4 • (х – 1)(х + 1) = 0;
б) (x + 2)2 – (x + 1)2 = 0
(х + 2 + х + 1)(х + 2 – х – 1) = 0
(2х + 3) • 1 = 0
2х + 3 = 0
2х = –3
х = –1,5;
в) (4x + 3)(16x2 – 12x + 9) = 9(7x3 + 3)
64х3 + 27 = 63х3 + 27
х3 = 0;
г) (2,6х – 3)(2,6x + 3) – (2,4x – 5)(2,4x + 5) = 2x(0,5x + 4)
6,76х2 – 9 – (5,76х2 – 25) = х2 + 8х
6,76х2 – 9 – 5,76х2 + 25 = х2 + 8х
х2 + 16 = х2 + 8х
8х = 16
х = 2;
г) (2x – 1)(4х2 + 2x + 1) = x(3x – 2)(3x + 2) – x3
8х3 – 1 = 9х3 – 4х – х3
–1 = –4х
х = –1 : (–4)
х = 0,25.
вправи поруч
