99999999 + 999999999=?
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9 . 1 + 9. 11 + 9.111 + 9.1111 + 9.11111 + 9.111111 + 9.1111111 + 9.11111111 + 9.111111111 + 9.1111111111
= (10-1) + (100 -1) + (1000-1) + (10000-1) + ............+ (10000000000-1)
= ( 10+100+1000+10000+..........+10000000000) - (1+1+1+1+..........+1+1)
=11111111110 - 1.10
=1111111100
= (10-1) + (100 -1) + (1000-1) + (10000-1) + ............+ (10000000000-1)
= ( 10+100+1000+10000+..........+10000000000) - (1+1+1+1+..........+1+1)
=11111111110 - 1.10
=1111111100
\(A=\frac{999999999}{2}-\frac{999999999}{3}-\frac{999999999}{6}\)
\(=\frac{999999999\cdot3-999999999\cdot2-999999999}{6}\)
\(=\frac{999999999\cdot3-999999999\cdot\left(2+1\right)}{6}\)
\(=\frac{999999999\cdot3-999999999\cdot3}{6}=\frac{0}{6}=0\)
vậy A=0
999*999*9.999*999.999.999*999*999.999.999=9.969.032.967.062.934.035.697.032.987.001
tớ ghi vậy cho dễ nhìn
99999999+999999999=1099999998
99999999 + 999999999=1099999998