( 1/Х ) + ( 1/y ) = 3/8
X + y = 12
Решение
( y + x )/ xy = 3/8
8( y + x ) = 3xy
y + x = ( 3/8 )xy
12 = ( 3/8 )xy
xy = 32
y = 32/x
X + ( 32/x ) = 12
X^2 + 32 = 12x
X^2 - 12x + 32 = 0
D = 144 - 128 = 16 = 4^2
X1 = ( 12 + 4 ) : 2 = 8
Х2 = ( 12 - 4 ) : 2 = 4
y = 32 / x
y1 = 32 / 8 = 4
y2 = 32 / 4 = 8
Ответ ( 8 ; 4 ) ; ( 4 ; 8 )