Răspuns:
Explicație pas cu pas:
b) __ __ __
B = 5xy + x3y + xy7
B = (500 + 10 x + y) +(100 x + 30 + y )+ (100 x + 10 y + 7)
B = ( 10 x + 100 x + 100 x ) + ( y + y + 10 y ) + ( 500 + 30 + 7 )
B = 210 x + 12 y + 537
B = 3 × ( 70 x + 4 y + 179 ) → divizibil cu 3
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c) __ __ __
C = xy + yz + zx
C = ( 10x + y) + (10y+z) +(10z+x)
C = ( 10 x + x) + ( 10y + y) + ( 10z + z )
C = 11 x + 11 y + 11 z
C = 11 × ( x + y + z ) → divizibil cu 11
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d) ___ ___ __ __
D = xy2 + yz3 + zt4 + tx1
D = (100x+10y+2) + ( 100y+10z+3) + (100z+10t+4) + (100t+10x+1)
D = ( 100x+10x) + (100y+10y) + (100z+10z) + (100t+10t) +(2+3+4+1)
D = 110 x + 110 y + 110z + 110 t + 10
D = 10 × ( 11 x + 11 y + 11 z + 11 t + 1 )
D = 2 × 5 × ( 11 x + 11 y + 11 z + 11 t + 1 ) → divizibil cu 5 ( un factor fiind 5)
