100+99-92-97+96+96-94-93+...+4+3-2-1
A=100+98+96+94+92+...+2-99-97-95-93-91-...-1 = ?
92+93+94+95+96+97+98+99+100
92 + 93 + 94 + 95 + 96 + 97 + 98 + 99 + 100
= (92 + 100) + (93 + 99) + (94 + 98) + (95 + 97) + 96
= 192 + 192 + 192 + 192 + 96
= 768 + 96
= 864
92 + 93 + 94 + 95 + 96 + 97 + 98 + 99 + 100 = 864
92+93+94+95+96+97+98+99+100=864
Tk cho mk nhé!
100-99+98-97+96-95+94-93+92-91+90
= ?
TÍNH NHANH
\(100-99+98-97+96-95+94-93+92-91+90\)
\(=\left(100-99\right)+\left(98-97\right)+\left(96-95\right)+\left(94-93\right)+\left(92-91\right)+90\)
\(=1+1+1+1+1+90\)
\(=95\)
Tính nhanh : 100 - 99 + 98 - 97 + 96 - 95 + 94 - 93 + 92 - 91 + 90
thấy (100-99)+(98-97)+(96-95)+(94-93)+(92-91)+90
=1+1+1+1+1+90
=95
100 - 99 + 98 - 97 + 96 - 95 + 94 - 93 + 92 - 91 + 90 = 95
100-99+98-97+96-95+94-93+92-91+90
=1+1+1+1+1+90
=95
100+99-98-97+96+95-94-93....+4+3-2-1 = ?
ta co neu nhu 99-98 thi con 1 cho den 2-1 van con1 vay ket qua day tinh la : 100+98/2+1=150 dap so 150
100+99-98-97+96+95-94-93+...+4+3-2-1
100+99-98-97+96+95-94-93+...+4+3-2-1
=100+(99-98-97+96)+(95-94-93+92)+...+(3-2-1)
=100+0+0+..+0
=100
Tính 1-2-3-4-5-6-7-8-9-10-...90-91-92-93-94-95-96-97-98-99
1-2-3-4-...-91-92-93-94-95-96-97-98-99=1-(2+3+4+5+..+97+98+99)
=1-[(2+99).(99-2+1):2]
=1-(101*98:2)
=1-4949
=-4948
a=100+99-98-97+96-95-94-93+...+4+3-2-1
A=100+99-98-97+96+95-94-93+.....+4+3-2-1
=> A=(100+99-98-97)+(96+95-94-93)+.........+(4+3-2-1)
=> A=4+4+...........+4 (có 25 số hạng)
=> A=4x25
=> A=100