Toán Giúp mik vs : 1.2 + 2.3 + 3.4 +….+ 99.100 Ngắn gọn hộ mik 05/07/2021 By Natalia Giúp mik vs : 1.2 + 2.3 + 3.4 +….+ 99.100 Ngắn gọn hộ mik
Gọi 1.2+2.3+3.4+4.5…+ 99.100 là A . Có : A=1 .2 + 2 . 3 + 3 . 4 + 4 . 5 +…+ 99 . 100 3A=1 . 2 . 3 + 2 . 3 . 3 + 3 . 4 . 3 + 4 . 5 . 3 +…+ 99 . 100 . 3 3A=1 . 2 . 3 + 2 . 3 .( 4 – 1 ) + 3 . 4 . ( 5 – 2 ) + 4 . 5 . ( 6 – 3 ) + … + 99 . 100 . ( 101 – 98 ) 3A=1 . 2 . 3 + 2 . 3 . 4 – 1 . 2 . 3 + 3 . 4 . 5 – 2 . 3 . 4 + 4 . 5 . 6 – 3 . 4 . 5 +…+ 99 . 100 . 101 – 98 . 99 . 100 3A= 99 . 100 . 101 A = $\frac{99.100.101}{3}$ A = 333 300 Trả lời
Đáp án: $A = 333 300$ Giải thích các bước giải: $\text{Gọi A = 1.2 + 2.3 + 3.4 +….+ 99.100}$ $\text{3A = 1.2.3 + 2.3.3 + 3.4.3 +…+ 99.100.3}$ $\text{3A = 1.2.3 + 2.3.(4-1) + 3.4.(5-2) + … + 99.100.(101-98)}$ $\text{3A = 1.2.3 + 2.3.4 – 1.2.3 + 3.4.5 – 2.3.4 +…+99.100.101 – 98.99.100 }$ $\text{3A = 99.100.101}$ $\text{A = 33.100.101 = 333 300}$ Trả lời
Gọi 1.2+2.3+3.4+4.5…+ 99.100 là A .
Có :
A=1 .2 + 2 . 3 + 3 . 4 + 4 . 5 +…+ 99 . 100
3A=1 . 2 . 3 + 2 . 3 . 3 + 3 . 4 . 3 + 4 . 5 . 3 +…+ 99 . 100 . 3
3A=1 . 2 . 3 + 2 . 3 .( 4 – 1 ) + 3 . 4 . ( 5 – 2 ) + 4 . 5 . ( 6 – 3 ) + … + 99 . 100 . ( 101 – 98 )
3A=1 . 2 . 3 + 2 . 3 . 4 – 1 . 2 . 3 + 3 . 4 . 5 – 2 . 3 . 4 + 4 . 5 . 6 – 3 . 4 . 5 +…+ 99 . 100 . 101 – 98 . 99 . 100
3A= 99 . 100 . 101
A = $\frac{99.100.101}{3}$
A = 333 300
Đáp án:
$A = 333 300$
Giải thích các bước giải:
$\text{Gọi A = 1.2 + 2.3 + 3.4 +….+ 99.100}$
$\text{3A = 1.2.3 + 2.3.3 + 3.4.3 +…+ 99.100.3}$
$\text{3A = 1.2.3 + 2.3.(4-1) + 3.4.(5-2) + … + 99.100.(101-98)}$
$\text{3A = 1.2.3 + 2.3.4 – 1.2.3 + 3.4.5 – 2.3.4 +…+99.100.101 – 98.99.100 }$
$\text{3A = 99.100.101}$
$\text{A = 33.100.101 = 333 300}$