x=2³⁷+2³⁸+2³⁹+2⁴⁰ x divizibil cu 15
x=2³⁷+2³⁸+2³⁹+2⁴⁰=2³⁷(2⁰+2¹+2²+2³)=2³⁷(1+2+4+8)=2³⁷×15 deci divizibil cu 15
y=2¹⁴³+2¹⁴⁴+....+2¹⁵⁰ y divizibil cu 30
y=2¹⁴³+2¹⁴⁴+....+2¹⁵⁰=2¹⁴²(2¹+2²+2³+2⁴+2⁵+2⁶+2⁷+2⁸) =
= 2¹⁴²(2+4+8+16+32+64+128+256)=2¹⁴² × 510=2¹⁴² × 17 ×30= deci divizibil cu 30
z= 2¹⁶+ 2¹⁷+2¹⁸+2¹⁹+3³¹+3³²+3³³+ 3³⁴ z divizibil cu 10
z= 2¹⁶+ 2¹⁷+2¹⁸+2¹⁹+3³¹+3³²+3³³+ 3³⁴=2¹⁵(2¹+2²+2³+2⁴)+3³¹(3⁰+3¹+3²+3³) =
=2¹⁵(2+4+8+16)+3³¹(1+3+9+27)=2¹⁵×30+3³¹×40=10(2¹⁵×3+3³¹×4) deci divizibil cu 10