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92
\(x+\dfrac{-7}{12}=\dfrac{17}{18}-\dfrac{1}{9}\)
\(x+\dfrac{-7}{12}=\dfrac{5}{6}\)
\(x=\dfrac{5}{6}-\dfrac{\left(-7\right)}{12}\)
\(x=\dfrac{10}{12}+\dfrac{7}{12}=\dfrac{17}{12}\)
93
\(\dfrac{-7}{15}-x=\dfrac{4}{5}+\dfrac{-2}{3}\)
\(\dfrac{-7}{15}-x=\dfrac{2}{15}\)
\(x=\dfrac{\left(-7\right)}{15}-\dfrac{2}{15}\)
\(x=-\dfrac{3}{5}\)
94
\(\dfrac{1}{2}-\left(x-\dfrac{5}{11}\right)=\dfrac{-3}{4}\)
\(x-\dfrac{5}{11}=\dfrac{1}{2}-\dfrac{-3}{4}\)
\(x-\dfrac{5}{11}=\dfrac{5}{4}\)
\(x=\dfrac{5}{4}+\dfrac{5}{11}\)
\(x=\dfrac{75}{44}\)
95
\(\dfrac{3}{4}+\left(\dfrac{2}{5}-x\right)=\dfrac{1}{4}\)
\(\dfrac{2}{5}-x=\dfrac{1}{4}-\dfrac{3}{4}\)
\(\dfrac{2}{5}-x=-\dfrac{1}{2}\)
\(x=\dfrac{2}{5}-\dfrac{-1}{2}\)
\(x=\dfrac{9}{10}\)
Bài 5:
n\(Na_2ZnO_2\) = \(\dfrac{8,58}{143}=0,06mol\)
n\(Mg_3\left(PO_4\right)_2\) =\(\dfrac{7,86}{262}=0,03mol\)
\(n_{CuSO_4}=\dfrac{7,42}{160}=0,046375\approx0,046mol\)
\(n_{CO_2}=\dfrac{26,88}{22,4}=1,2mol\)
\(n_{NO}=\dfrac{20,16}{22,4}=0,9mol\)
\(n_{NO_2}=\dfrac{16,8}{22,4}=0,75mol\)
\(n_{CuSO_4}=\dfrac{1,2.10^{23}}{6.10^{23}}=0,2mol\)
\(n_{Fe}=\dfrac{4,8.10^{23}}{6.10^{23}}=0,8mol\)
n\(Na_3PO_4\) = \(\dfrac{15,3.10^{23}}{6.10^{23}}=2,55mol\)
7: 3x^2+mx+5 chia hết cho x+2
=>3x^2+6x+(m-6)x+2m-12-2m+17 chia hết cho x+2
=>-2m+17=0
=>m=17/2
8: x^2-4x+m chia hết cho x-5
=>x^2-5x+x-5+m+5 chia hết cho x-5
=>m+5=0
=>m=-5
7:
A+B
\(=x^4-2xy+y^2+y^2+2xy+x^2+1\)
=x^4+2y^2+x^2+1
A-B
=x^4-2xy+y^2-y^2-2xy-x^2-1
=x^4-4xy-x^2-1
5:
a: =8x^2-4x^2=4x^2
b: =(5-7)*x^2y^3z^3=-2x^2y^3z^3
c: =(3+2-1/3-1/2-1/6)*x^2y^2
=4x^2y^2
11. political correspondent
12. tropical
13. separated
14. independent
15. Foreign / hospitality / friendliness
16. modernized
17. equally
18. independent
19. industrial
20. inconvenient
21. fashionably
22. officially
23. introduction
24. worn out
25. instructions
26. religious beliefs
27. poets
28. uncomfortableness / dirtiness
29. division
30. symbolizes