mình đây

a11.62+(-12).11+50.11

=11.(62+(-12)+50)

=11.(50+50)

11.100=1100

b5/13+-5/7+-20/41+8/13+21/41

=(5/13+8/13)+(-20/41+21/41)+-5/7

=1+1/41+-5/7

=89/287

nhớ tích đúng nha

a, 11.62+(-12).11+50.11

= 11.[62+(-12)+50]

= 11.100 = 1100

b, 5/13 + -5/7 + -20/41 + 8/13 + 21/41

= ( 5/13 + 8/13 ) + [ -20/41 + 21/41 ] + -5/7

= 1 + 1/41 + -5/7

= 89/287

a 15/7"3/4

dễ, nhưng phai giai dc câu nay  60% nhan x cong 2 phan 3 = 1 phan 3 nhan 6va 1 phan 3

dễ mà

     Bài 1:

(\(x-12\))⁸⁰ + (y + 15)⁴⁰ = 0

Vì (\(x-12\))⁸⁰ ≥ 0 ∀ \(x\); (y + 15)⁴⁰ ≥ 0 ∀ y

Vậy (\(x-12\))⁸⁰ + (y + 15)⁴⁰  = 0 

⇔ \(\left\{{}\begin{matrix}x-12=0\\y+15=0\end{matrix}\right.\)

⇒ \(\left\{{}\begin{matrix}x=12\\y=-15\end{matrix}\right.\)

Vậy \(\left(x;y\right)\) = (12; -15)

      Bài 2:

      \(\dfrac{x}{y}\) = \(\dfrac{a}{b}\) (đk \(y;b\ne0\))

   ⇒ \(\dfrac{x}{a}\) =  \(\dfrac{y}{b}\) 

Áp dụng tính chất dãy tỉ số bằng nhau ta có:

      \(\dfrac{x}{a}\) = \(\dfrac{y}{b}\) = \(\dfrac{x-y}{a-b}\) 

   ⇒ \(\dfrac{x}{a}\) = \(\dfrac{x-y}{a-b}\)

  ⇒ \(\dfrac{x-y}{x}\) = \(\dfrac{a-b}{a}\) (đpcm)

\(\frac{7}{13}.\frac{5}{9}+\frac{7}{19}.\frac{8}{13}-3.\frac{7}{19}=\)\(\frac{-1288}{2223}\)

Kết quả = -1288/2223

Đề bài kiểu j vậy :<

bạn ghi rõ số ra đi

a; \(\dfrac{3}{5}\) - \(\dfrac{-7}{10}\) - \(\dfrac{13}{-20}\)

= \(\dfrac{12}{20}\) +  \(\dfrac{14}{20}\) + \(\dfrac{13}{20}\)

= \(\dfrac{39}{20}\)

b; \(\dfrac{1}{2}\) + \(\dfrac{1}{-3}\) + \(\dfrac{1}{4}\) - \(\dfrac{-1}{6}\)

= \(\dfrac{6}{12}\) - \(\dfrac{4}{12}\) + \(\dfrac{3}{12}\) + \(\dfrac{2}{12}\)

= \(\dfrac{7}{12}\)

bn viết p/s hoặc dùng / cho dễ

\(\frac{4}{5}\cdot\frac{3}{7}+\frac{4}{5}\cdot\frac{6}{7}-\frac{4}{5}\cdot\frac{4}{14}\)

\(=\frac{4}{5}\cdot\left(\frac{3}{7}+\frac{6}{7}-\frac{4}{14}\right)\)

\(=\frac{4}{5}\cdot1=\frac{4}{5}\)

                                                                     #Louis