Question

[Nguyễn Thị Mai]

BÀI 1 THỰC HIỆN PHÉP TÍNH :

A, \(\frac{25}{4}\)+\(\frac{-5}{4}\)          B,\(\frac{-5}{9}\)+\(\frac{-2}{7}\)         C,\(\frac{1}{4}\)+\(\frac{9}{11}\)+\(\frac{7}{4}\)+\(\frac{-2}{11}\)         D,\(\frac{-5}{19}\)*\(\frac{8}{19}\)+\(\frac{-14}{19}\)*\(\frac{11}{19}\)

BÀI 2: TÌM X BIẾT

A, X+\(\frac{5}{9}\)=\(\frac{-8}{9}\)       B,\(\frac{-1}{8}\)-X=\(\frac{9}{20}\)         C,( X + 5)\(^3\)-12=15                 D,/X-3/-\(\frac{4}{15}\)=\(\frac{26}{15}\)

Answer 1

[Royan]

Bài 1:

a) \(\frac{25}{4}+\frac{-5}{4}=\frac{25-5}{4}=\frac{20}{4}=5\)

b)\(\frac{-5}{9}+\left(\frac{-2}{7}\right)=\frac{-35}{63}+\left(\frac{-18}{63}\right)=\frac{-53}{63}\)

c) \(\frac{1}{4}+\frac{9}{11}+\frac{7}{4}+\left(\frac{-2}{11}\right)=\left(\frac{1}{4}+\frac{7}{4}\right)+\left(\frac{-2}{11}+\frac{9}{11}\right)=2+\frac{7}{11}=\frac{22+7}{11}=\frac{29}{11}\)

d) \(\frac{-5}{19}.\frac{8}{19}+\left(\frac{-14}{19}\right).\frac{11}{19}=\frac{-40}{361}-\frac{151}{361}=-\frac{191}{361}\)

Answer 2

[Royan]

Bài 2: 

a) \(x+\frac{5}{9}=\frac{-8}{9}\)  \(\Leftrightarrow x=\frac{-8}{9}-\frac{5}{9}\)  \(\Leftrightarrow x=-\frac{13}{9}\)

b) \(\frac{-1}{8}-x=\frac{9}{20}\)  \(\Leftrightarrow x=\frac{-1}{8}-\frac{9}{20}\)  \(\Leftrightarrow x=\frac{-5}{40}-\frac{18}{40}\)  \(\Leftrightarrow x=-\frac{23}{40}\)

c) (x + 5)³ - 12 = 15

\(\Leftrightarrow\)(x + 5)³ = 27

\(\Leftrightarrow\)x + 5 = 3

\(\Leftrightarrow\)x = -2

d) \(\left|x-3\right|-\frac{4}{15}=\frac{26}{15}\)  \(\Leftrightarrow\left|x-3\right|=2\)  \(\Leftrightarrow\orbr{\begin{cases}x-3=2\\x-3=-2\end{cases}}\)  \(\Leftrightarrow\orbr{\begin{cases}x=5\\x=1\end{cases}}\)