a) 2x-1|21 => 2x+1∈{-21,-7,-3,-1,1,3,7,21}=> x∈{-11,-4,-2,-1,0,1,3,10}
dar x este numar natural=>
=>x∈{0,1,3,10}
b) (2×-1)|(8×+6)
(2x-1)|(8x+6)
dar (2x-1)|(8x-4) => (2x-1)|8x+6-8x+4 => (2x-1)|10
=> 2x-1∈{-10,-5,-2,-1,1,2,5,10} <=> x∈{-[tex] \frac{9}{4} [/tex] , -2, -[tex] \frac{1}{2} [/tex] , 0, [tex] \frac{3}{2} [/tex] , 3, [tex] \frac{11}{2} [/tex] }
dar x este numar natural=> x∈{ 0,3}
c) (3x-2)|(5×+3)
(3x-2)|(5x+3)=> (3x-2)|(15x+9)
dar (3x-2)|(15x-10)
=> (3x-2)|19 => 3x-2∈{-19,-1,1,19} => x∈{-[tex] \frac{17}{3} [/tex] , [tex] \frac{1}{3} [/tex] , 1, 7}
dar x este numar natural => x∈{1,7}
d) (×-1)|(×+7)
(x-1)|(x+7)
dar (x-1)|(x-1)
=> (x-1)| 8 => x-1∈{-8,-4,-2,-1,1,2,4,8} => x∈{-7,-3,-1,0,2,3,5,9}
dar x este numar natural=> x∈{0,2,3,5,9}
