5. Ta có: x.Ca + 2.P+ 8.O = 310

\(\)<=> 40x + 62 + 128 = 310

<=> 40x = 120

<=> x = 3

CTHH của hợp chất: Ca3(PO4)2

6. Ta có : x.Na + S + 4.O = 142

<=> 23x + 32 + 64 = 142

<=> 23x = 46

<=> x = 2

CTHH của hợp chất là Na₂SO₄

7. Ta có: Zn + x.N + 3x.O = 189

<=> 65 + 14x + 48x = 189

<=> (14 + 48).x = 124

<=> x = 2

CTHH hợp chất là Zn(NO₃)₂

Các câu 8, 9, 10 bạn tự làm nhé, giống hệt cách làm chỉ thay số vào thôi ~!

5) Ca₃(PO₄)₂

6) Na₂SO₄

7) Zn(NO₃)₂

8) Cu(NO₃)₂

9) K₃PO₄

10) Al(NO₃)₃

2.Tính

a) 3/7 nhân 4=12/7              b) 2/3 nhân 1=2/3       c) 6/11 nhân 0=0

d)2 nhân 4/7=8/7                e) 1 nhân 3/8=3/8      g) 0 nhân 13/18=0

Chúc e học tốt

2.Tính

a) 3/7 nhân 4=12/7             b) 2/3 nhân 1=2/3     c) 6/11 nhân 0=0

d)2 nhân 4/7=8/7             e) 1 nhân 3/8=3/8        g) 0 nhân 13/18=0

a) = 12/7

b) = 2/3

c) = 0

d) = 8/7

e) = 3/8

g) = 0

\(\frac{1}{3}:x-\frac{2}{3}=\frac{5}{6}+\frac{7}{8}\)

\(\frac{1}{3}:x-\frac{2}{3}=\frac{41}{24}\)

\(\frac{1}{3}:x=\frac{19}{8}\)

\(x=\frac{8}{57}\)

\(\frac{2}{5}-x:\frac{3}{5}=\frac{6}{7}\)

\(x:\frac{3}{5}=\frac{-16}{35}\)

\(x=\frac{-48}{175}\)

\(\frac{4}{5}-\frac{26}{m}=\frac{-8}{15}\)

\(\frac{26}{m}=\frac{4}{3}\)

=> 26 x 3 = m x 4

   78 = m x 4

         m = 19,5

Câu 1 :\(\frac{1}{3}\div x-\frac{2}{3}=\frac{5}{6}+\frac{7}{8}\)

\(\Leftrightarrow\frac{1}{3x}=\frac{5}{6}+\frac{7}{8}+\frac{2}{3}\)

\(\Leftrightarrow\frac{1}{3x}=\frac{4\cdot5}{24}+\frac{7\cdot3}{24}+\frac{2\cdot8}{24}\)

\(\Leftrightarrow\frac{1}{3x}=\frac{20}{24}+\frac{21}{24}+\frac{16}{24}\)

\(\Leftrightarrow\frac{1}{3x}=\frac{57}{24}\)

\(\Leftrightarrow24=57\cdot3x\)

\(\Leftrightarrow24=171x\)

\(\Leftrightarrow x=\frac{24}{171}=\frac{8}{57}\)

Câu 2: \(\frac{2}{5}-x\div\frac{3}{5}=\frac{6}{7}\)

\(\Leftrightarrow\frac{-5x}{3}=\frac{6}{7}-\frac{2}{5}\)

\(\Leftrightarrow\frac{-5x}{3}=\frac{5\cdot6}{35}-\frac{2\cdot7}{35}\)

\(\Leftrightarrow\frac{-5x}{3}=\frac{30}{35}-\frac{14}{35}\)

\(\Leftrightarrow-\frac{5x}{3}=\frac{16}{35}\)

\(\Leftrightarrow-175x=48\)

\(\Leftrightarrow x=-\frac{48}{175}\)

Câu 3: \(\frac{4}{5}-\frac{26}{m}=-\frac{8}{15}\)

\(\Leftrightarrow\frac{26}{m}=\frac{4}{5}-\left(-\frac{8}{15}\right)\)

\(\Leftrightarrow\frac{26}{m}=\frac{4}{5}+\frac{8}{15}\)

\(\Leftrightarrow\frac{26}{m}=\frac{12}{15}+\frac{8}{15}\)

\(\Leftrightarrow\frac{26}{m}=\frac{20}{15}\)

\(\Leftrightarrow20m=26\cdot15=390\)

\(\Leftrightarrow m=\frac{390}{20}=\frac{39}{2}\)

1+1+2+2+3+3+4+4+5+5+6+6+7+7+8+8+9+9+10+10 = 110

HT

=110 nha

HT

= 110 nhé

7/8 + 3/4=13/8

3/2 + 4/5=23/10

6/7 * 5/6=5/7

5/6 : 8/9=15/16

\(\frac{7}{8}+\frac{3}{4}=\frac{28}{32}+\frac{24}{32}=\frac{52}{32}\)

\(\frac{3}{2}+\frac{4}{5}=\frac{15}{10}+\frac{8}{10}=\frac{23}{10}\)

\(\frac{6}{7}x\frac{5}{6}=\frac{30}{42}\)

\(\frac{5}{6}:\frac{8}{9}=\frac{5}{6}x\frac{9}{8}=\frac{45}{48}\)

\(\frac{7}{8}+\frac{3}{4}=\frac{13}{8}\)

\(\frac{3}{2}+\frac{4}{5}=\frac{23}{10}\)

\(\frac{6}{7}.\frac{5}{6}=\frac{5}{7}\)

\(\frac{5}{6}:\frac{8}{9}=\frac{15}{16}\)

đây mà là toán lớp 1 à.đồ dở hơi.

ban a toán lớp mấy thì  toán vậy bạn có trả lời được ko mà còn ra vẻ hả bạn 'doraemi'

dúng rồi đó ko trả lời thì thôi 

1.3.77−1​+3.7.99−3​+7.9.1313−7​+9.13.1515−9​+\frac{19-13}{13.15.19}+13.15.1919−13​

=\frac{1}{1.3}-\frac{1}{3.7}+\frac{1}{3.7}-\frac{1}{7.9}+\frac{1}{7.9}-\frac{1}{9.13}+\frac{1}{9.13}-\frac{1}{13.15}+\frac{1}{13.15}-\frac{1}{15.19}=1.31​−3.71​+3.71​−7.91​+7.91​−9.131​+9.131​−13.151​+13.151​−15.191​

=\frac{1}{1.3}-\frac{1}{15.19}=\frac{95}{285}-\frac{1}{285}=\frac{94}{285}=1.31​−15.191​=28595​−2851​=28594​

b,=\frac{1}{6}.\left(\frac{6}{1.3.7}+\frac{6}{3.7.9}+\frac{6}{7.9.13}+\frac{6}{9.13.15}+\frac{6}{13.15.19}\right)b,=61​.(1.3.76​+3.7.96​+7.9.136​+9.13.156​+13.15.196​)

làm giống như trên

c,=\frac{1}{8}.\left(\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+...+\frac{1}{48.49.50}\right)c,=81​.(1.2.31​+2.3.41​+3.4.51​+...+48.49.501​)

=\frac{1}{16}.\left(\frac{2}{1.2.3}+\frac{2}{2.3.4}+\frac{2}{3.4.5}+...+\frac{2}{48.49.50}\right)=161​.(1.2.32​+2.3.42​+3.4.52​+...+48.49.502​)

=\frac{1}{16}.\left(\frac{3-1}{1.2.3}+\frac{4-2}{2.3.4}+\frac{5-3}{3.4.5}+...+\frac{50-48}{48.49.50}\right)=161​.(1.2.33−1​+2.3.44−2​+3.4.55−3​+...+48.49.5050−48​)

=\frac{1}{16}.\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+\frac{1}{3.4}-\frac{1}{4.5}+...+\frac{1}{48.49}-\frac{1}{49.50}\right)=161​.(1.21​−2.31​+2.31​−3.41​+3.41​−4.51​+...+48.491​−49.501​)

=\frac{1}{16}.\left(\frac{1}{2}-\frac{1}{2450}\right)=\frac{1}{16}.\left(\frac{1225}{2450}-\frac{1}{2450}\right)=\frac{153}{4900}=161​.(21​−24501​)=161​.(24501225​−24501​)=4900153​

d,=\frac{5}{7}.\left(\frac{7}{1.5.8}+\frac{7}{5.8.12}+\frac{7}{8.12.15}+...+\frac{7}{33.36.40}\right)d,=75​.(1.5.87​+5.8.127​+8.12.157​+...+33.36.407​)

=\frac{5}{7}.\left(\frac{8-1}{1.5.8}+\frac{12-5}{5.8.12}+\frac{15-8}{8.12.15}+...+\frac{40-33}{33.36.40}\right)=75​.(1.5.88−1​+5.8.1212−5​+8.12.1515−8​+...+33.36.4040−33​)

=\frac{5}{7}.\left(\frac{1}{1.5}-\frac{1}{5.8}+\frac{1}{5.8}-\frac{1}{8.12}+\frac{1}{8.12}-\frac{1}{12.15}+...+\frac{1}{33.36}-\frac{1}{36.40}\right)=75​.(1.51​−5.81​+5.81​−8.121​+8.121​−12.151​+...+33.361​−36.401​)

=\frac{5}{7}.\left(\frac{1}{5}-\frac{1}{1440}\right)=\frac{5}{7}.\left(\frac{288}{1440}-\frac{1}{1440}\right)=\frac{41}{288}=75​.(51​−14401​)=75​.(1440288​−14401​)=28841​

P/S: . là nhân nha