a; -\(\dfrac{4}{9}.\dfrac{7}{15}+\dfrac{4}{-9}.\dfrac{8}{15}\)

= - \(\dfrac{4}{9}\).(\(\dfrac{7}{15}+\dfrac{8}{15}\))

= - \(\dfrac{4}{9}\).1

= - \(\dfrac{4}{9}\)

b; - \(\dfrac{5}{4}.\dfrac{16}{25}\) + \(\dfrac{-5}{4}\).\(\dfrac{9}{25}\)

= - \(\dfrac{5}{4}\).(\(\dfrac{16}{25}\) + \(\dfrac{9}{25}\))

= - \(\dfrac{5}{4}\). 1

= - \(\dfrac{5}{4}\)

c; \(-\dfrac{5}{12}.\dfrac{4}{19}\) + \(\dfrac{-7}{12}.\dfrac{4}{19}-\dfrac{40}{57}\)

= - \(\dfrac{5}{12}\).\(\dfrac{4}{19}\) - \(\dfrac{7}{12}\).\(\dfrac{4}{19}\) - \(\dfrac{4}{19}\).\(\dfrac{10}{3}\)

= - \(\dfrac{4}{19}\).(\(\dfrac{5}{12}\) + \(\dfrac{7}{12}\) + \(\dfrac{10}{3}\))

= - \(\dfrac{4}{19}\).\(\dfrac{13}{3}\)

= - \(\dfrac{52}{57}\)

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

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

= \(\dfrac{39}{20}\)

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

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

= \(\dfrac{7}{12}\)

TL

4/7-2/15:4/25=4/7-5/6=-11/42 

nha

HT

\(\frac{4}{7}-\frac{2}{15}\div\frac{4}{25}\)

\(=\frac{4}{7}-\frac{2}{15}\times\frac{25}{4}\)

\(=\frac{4}{7}-\frac{50}{60}\)

\(=\frac{4}{7}-\frac{5}{6}\)

\(=\frac{24}{42}-\frac{35}{42}\)

\(=-\frac{11}{42}\)

11/42 nha

31/2+45/7-55/14  ?

\(\dfrac{20}{7}\)

    31/2+45/7-55/14 
= 217/14+90/14-55/14
= 252/14
^{_{Rồi tự rút gọn(Nếu được)}}
 

\(3\frac{1}{2}+4\frac{5}{7}-5\frac{5}{14}=\frac{7}{2}+\frac{33}{7}-\frac{75}{14}=\frac{49}{14}+\frac{66}{14}-\frac{75}{14}=\frac{40}{14}=\frac{20}{7}\)

#Fox

????????????????????????????????????!?¿??¿???¿??????????¿??¿?????????????????????

=20/7

Bạn chỉ giúp mk cách làm được ko ạ

20/7 nha

     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)

    Bài 3:

3⁴⁰⁰ và 2³⁰⁰

3⁴⁰⁰  = (3⁴)¹⁰⁰ = 81¹⁰⁰ 

2³⁰⁰ = (2³)¹⁰⁰ = 8¹⁰⁰ 

Vì 3⁴ > 2⁴ > 2³ ⇒ (3⁴)¹⁰⁰ > (2³)¹⁰⁰ 

Vậy 3⁴⁰⁰ > 2³⁰⁰ 

a; 0,2.\(\dfrac{15}{36}\) - (\(\dfrac{2}{5}\) + \(\dfrac{2}{3}\)): 1%

   = \(\dfrac{1}{12}\)  - \(\dfrac{16}{15}\): \(\dfrac{1}{100}\)

  =    \(\dfrac{1}{12}\) - \(\dfrac{320}{3}\)

= \(\dfrac{1}{12}\) - \(\dfrac{1280}{12}\)
= - \(\dfrac{1279}{12}\)

b; 75% - 1\(\dfrac{1}{2}\) + 0,5 : \(\dfrac{5}{12}\)

= 0,75 - 1,5 + 1,2

= -0,75 + 1,2

= 0,45

c; 1\(\dfrac{3}{15}.0,75-\left(\dfrac{8}{15}+0,25\right)\).\(\dfrac{24}{47}\)

= \(\dfrac{28}{15}\).0,75 - \(\dfrac{47}{60}\).\(\dfrac{24}{47}\)

= \(\dfrac{7}{5}-\dfrac{2}{5}\)

= 1

d; \(\dfrac{32}{15}\): (-1\(\dfrac{1}{5}\) + 1\(\dfrac{1}{3}\))

= \(\dfrac{32}{15}\): (-\(\dfrac{6}{5}\) + \(\dfrac{4}{3}\))

= \(\dfrac{32}{15}\): \(\dfrac{2}{15}\)

= 16

e; 20 + 9\(\dfrac{1}{4}:2\dfrac{1}{4}\)

= 20 + \(\dfrac{37}{4}\) : \(\dfrac{9}{4}\)

= 20 + \(\dfrac{37}{9}\)

= \(\dfrac{217}{9}\)

g; \(\dfrac{3}{4}.\dfrac{16}{9}\)- \(\dfrac{7}{5}\): (-\(\dfrac{21}{20}\))

=  \(\dfrac{4}{3}\) - (-\(\dfrac{4}{3}\))

= \(\dfrac{4}{3}\) + \(\dfrac{4}{3}\)

= \(\dfrac{8}{3}\)

1+ \(\frac{10}{4}\)+ \(\frac{10}{12}\)+ \(\frac{10}{24}\)+ \(\frac{10}{40}\)+ \(\frac{10}{60}\)= \(\frac{31}{6}\).

kết quả bằng 161/30

8/3 nha bạn

k mik nhé