x-y=1 y=1+x y=1+x y=1+x y=1+x
xy=240 x(1+x)=240 x+x^2=240 x^2+x-240=0 (x+15)(x+16)=0
x2 + x - 240 = 0
D = b2 - 4ac
D = 1 + 960 = 961 = 31
x1,2 = -b ± √D/2a
x1 = -1 + 31/2= 30/2 = 15
x2 = -1 - 31/2 = - 32/2 = -16
ответ: x1 = 15; x2 = -16
1) 18 - 16х = -30х - 10, 2) -7х + 2 = 3х - 1, 3) 10 - 2х = 12 - х,
-16х + 30х = -10 - 18, -7х - 3х = -1 - 2, -2х + х = 12 - 10,
14х = -28, -10х = -3, -х = 2,
х = -28 : 14, х = -3 : (-10), х = -2;
х = -2; х = 0,3;
4) 6х - 19 = -2х - 15, 5) 0,2х + 3,4 = 0,6х - 2,6, 6) 5/6х + 12 = 1/4х - 2,
6х + 2х = -15 + 19, 0,2х - 0,6х = -2,6 - 3,4, 12(5/6х + 12) = 12(1/4х - 2),
8х = 4, -0,4х = -6, 10х + 144 = 3х - 24,
х = 4 : 8, х = -6 : (-0,4), 10х - 3х = -24 - 144,
х = 0,5; х = 15; 7х = -168,
х = -168 : 7,
х = -24.
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