`19,8 xx 2/6`

`=99/5 xx 2/6`

`= (99xx2)/(5xx6)`

`=198/30`

`=33/5`

= \(\dfrac{33}{5}\) hoặc 6.6

=7/19.8/11

=56/209

\(\frac{7}{19}.\frac{8}{11}+\frac{7}{19}\)

\(=\frac{7}{19}.\frac{8}{11}+\frac{7}{19}.1\)

\(=\frac{7}{19}.\left(\frac{8}{11}+1\right)\)

\(=\frac{7}{19}.\frac{19}{11}\)

\(=\frac{7}{11}\)

\(\dfrac{-13}{19}.\dfrac{8}{25}+\dfrac{13}{19}.\dfrac{-17}{25}\)

= \(\left(\dfrac{-13}{19}+\dfrac{13}{19}\right)x\left(\dfrac{8}{25}-\dfrac{-17}{25}\right)\)

=\(0.1=0\)

sai rồi

\(A=\dfrac{7}{19}\cdot\dfrac{8}{11}+\dfrac{7}{19}\cdot\dfrac{3}{11}+\dfrac{12}{19}\\ A=\dfrac{7}{19}\left(\dfrac{8}{11}+\dfrac{3}{11}\right)+\dfrac{12}{19}\\ A=\dfrac{7}{19}\cdot1+\dfrac{12}{19}\\ A=\dfrac{19}{19}=1\)

A = 7/19.8/11+7/19.3/11+12/19

A = 7/19. . (8/11 + 3/11) + 12/19

A = 7/19 . 1 + 12/19

A = 7/19 + 12/19

A = 1

A=7/19.8/11+7/19.3/11+12/19

A=7/19.(8/11+3/11)+12/19

A=7/19.1+12/19

A=7/19+12/19

A=1

Ai có lòng tốt

cho mình một 

tích đúng nhé.

Bài làm 

\(A=\frac{7}{19}.\frac{8}{11}+\frac{7}{19}.\frac{3}{11}+\frac{12}{19}\)

\(A=\frac{7}{19}.\left(\frac{8}{11}+\frac{3}{11}\right)+\frac{12}{19}\)

\(A=\frac{7}{19}.1+\frac{12}{19}\)

\(A=\frac{7}{19}+\frac{12}{19}\)

\(A=1\)

A=(17+2).8^2+17

A=17.8^2+2.8^n+17A=17.(8^n+1)+2.8^n

vi 8^n la so chan nen 8^n+1 la so le

ta co 17 la so le

suy ra 17.8^n la hop so

ma 2.8^2 la hop so

suy ra A la hop so