Question

A=1.3+2.4+3.5+...+97.99+98.100

CÁC CẬU GIẢI HỘ GIÚP MK NHA AI NHANH MK TICK CHO

MÀ DẤU . LÀ DẤU NHÂN NHA

Answer 1

A = 1( 2+1 ) + 2( 3+1 ) + 3( 4+1 ) +...+ 97( 98+1 ) + 98( 99+1 )

A = 1.2 + 1.1 + 2.3 + 2.1 + 3.4 + 3.1 +...+ 97.98 +97.1 + 98.99 + 98.1

A = ( 1.2 + 2.3 + 3.4 +...+ 97.98 + 98.99 ) + ( 1 + 2 + 3 +....+ 97 + 98)

A = 323400 + 4851 = 328251

Answer 2

ghi vậy mới đúng

Answer 3

Đúng rồi đó

Answer 4

(1.2+2.3+3.4....97.98+98.99)+(1+2+3+..+98)

=323400+4851=328251

Answer 5

A=1.3+2.4+3.5+...+97.99+98.100

A=1.(2+1)+2.(3+1)+3.(4+1)+...+97.(98+1)+98.(99+1)

A=1.2+1+2.3+2+3.4+3+...+97.98+97+98.99+98

A=(1.2+2.3+3.4+...+98.99)+(1+2+3+...+98)

Đặt B=1.2+2.3+3.4+...+98.99

3B=1.2.3+2.3.3+3.4.4+...+98.99.3

=1.2.3+2.3.(4-1)+3.4.(5-2)+...+98.99.(100-97)

=1.2.3+2.3.4-1.2.3+3.4.5-2.3.4+...+98.99.100-97.98.99

=98.99.100

B=98.99.100) :3

Vậy A=\(\frac{98.99.100}{3}+\frac{98.99}{2}=328251\)

Answer 6

(1.2+2.3+3.4....97.98+98.99)+(1+2+3+..+98)

=323400+4851=328251

Answer 7

(1.2+2.3+3.4....97.98+98.99)+(1+2+3+..+98)

=323400+4851=328251