a) \(12.79-64.37+12.21-36.37+12000\)

\(=\left(12.79+12.21\right)-\left(64.37+36.37\right)+12000\)

\(=\left[12\left(79+21\right)-37\left(64+36\right)+12000\right]\)

\(=12.100-37.100+12000\)

\(=1200-3700+12000\)

\(=9500\)

b) \(112.39+1237+112.61\)

\(=\left(112.39+112.61\right)+1237\)

\(=112\left(39+61\right)+1237\)

\(=112.100+1237\)

\(=11200+1237\)

\(=12437\)

c) \(35.762+351-35.662\)

\(=35\left(762-662\right)+351\)

\(=35.100+351\)

\(=3500+351\)

\(=3851\)

d) \(\frac{20}{4}-\frac{5^9}{5^8}=5-5=0\)

e) \(\left(\frac{5^{19}}{5^{17}}-4\right):7=\left(5^2-4\right):7=21:7=3\)

f)  \(\frac{84}{4}+\frac{3^9}{3^7}+5^0=21+3^2+1=31\)

gõ đề bài trên google rùi e chép là dc ok

giải hộ thôi đề bài ở trường THCS Nguyễn Đức Cảnh đó.

tớ cũng có đề bài giống nguyễn thị bích ngọc các cậu giải cho tớ nhé

Ai hởHoàng Quốc Việt

20.B

21.B

20 B

21 B

a) 3^10+3^11=3^10 x(1+3)

                  =3^10 x4

=> 3^10+3^11 chia hết cho 4

thang nay rot vl

1; = ( -4/10 + 3/10 ) : ( -2/5 + 2/3 ) = -1/10 : ( -6/15 + 10/15 ) = -1/10 : 4/15 = -1/10 . 15/4 = -15/40 = -3/8

2; = 25/2 . -5/7 + 39/4 + -3/2 . 5/7 = -125/14 + 39/4 + -15/14 = ( -125/14 + -15/14 ) + 39/4 = -10 + 39/4 = -40/4 + 39/4 = -1/4

3; = 5/52 + 35/52 + 40/52 = 40/52 + 40/52 = 80/52 = 20/13

4; = ( -39/52 + 20/52 ) . 7/2 - ( 117/52 + 32/52 ) . 7/2 = -19/52 . 7/2 - 149/52 . 7/2 = ( -19/52 + -149/52 ) . 7/2 = -168/52 .7/2 = -147/13

5; = ( 36/12 + -9/12 + 8/12 ) - ( -12/6 + -8/6 + -9/6 ) - ( 6/6 - 14/6 - 27/6 ) = 35/12 + 10/12 + 70/12 = 115/12

6; = -1/3 + -8/35 +-2/9 + -1/135 +4/5 +-4/9 +3/7 = (-1/3 + -2/9 + -4/9 ) + ( -8/35 + 4/5 + 3/7 ) + -1/135 = ( -1/3 + -2/3 ) + ( -8/35 + 28/35 + 15/35 ) + -1/135 = -1 + 1 + -1/135 = -1/135

1) Ta có: \(\frac{-4}{7}-\frac{11}{19}+\frac{13}{19}\cdot\frac{-3}{7}+\frac{2}{19}:\frac{-7}{4}\)

\(=\frac{-4}{7}-\frac{11}{19}-\frac{39}{133}-\frac{8}{133}\)

\(=\frac{-76}{133}-\frac{77}{133}-\frac{39}{133}-\frac{8}{133}\)

\(=\frac{-200}{133}\)

2) Ta có: \(\left(\frac{-4}{9}+\frac{3}{5}\right):\frac{1}{\frac{1}{5}}+\left(\frac{1}{5}-\frac{5}{9}\right):\frac{1}{\frac{1}{5}}\)

\(=\left(\frac{-4}{9}+\frac{3}{5}\right)\cdot\frac{1}{5}+\left(\frac{1}{5}-\frac{5}{9}\right)\cdot\frac{1}{5}\)

\(=\frac{1}{5}\left(\frac{-4}{9}+\frac{3}{5}+\frac{1}{5}-\frac{5}{9}\right)\)

\(=\frac{1}{5}\left(-1+\frac{4}{5}\right)\)

\(=\frac{1}{5}\cdot\frac{-1}{5}=\frac{-1}{25}\)

3) Ta có: \(\frac{4}{5}-\left(-\frac{2}{7}\right)-\frac{7}{10}\)

\(=\frac{4}{5}+\frac{2}{7}-\frac{7}{10}\)

\(=\frac{56}{70}+\frac{20}{70}-\frac{49}{70}\)

\(=\frac{27}{70}\)

4) Ta có: \(\frac{2}{7}-\left(-\frac{13}{15}+\frac{4}{9}\right)-\left(\frac{5}{9}-\frac{2}{15}\right)\)

\(=\frac{2}{7}+\frac{13}{15}-\frac{4}{9}-\frac{5}{9}+\frac{2}{15}\)

\(=\frac{2}{7}+1-1=\frac{2}{7}\)

Bạn ơi câu 2 : 1\1\5 là hỗn số mà bạn