Chỉ em 25 đến 36 với ạ
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7668:36=213
8527:25= 341,08
1715:49=35
20700:3=6900

Bài 26:
Ta có: A+B+C
\(=4x^2-5xy+3y^2+3x^2+2xy+y^2-x^2+3xy+2y^2\)
\(=6x^2+6y^2\)
Ta có: B-C-A
\(=3x^2+2xy+y^2-4x^2+5xy-3y^2+x^2-3xy-2y^2\)
\(=4xy-4y^2\)
Ta có: C-A-B
\(=-x^2+3xy+2y^2-4x^2+5xy-3y^2-3x^2-2xy-y^2\)
\(=-8x^2-6xy-2y^2\)

Bài 2:
\(\sqrt{2x-1}=5\)
=> 2x - 1 = 25
=> 2x = 26
=> x = 13
b) \(\sqrt[3]{3x+2}=-3\)
=> 3x + 2 = -27
=> 3x = -29
=> x = -29/3
P/s: Mỗi lần chỉ đc hỏi 1 bài thôi em nehs!
1. ĐK:
a, \(x\ge\dfrac{5}{2}\)
b, \(\left\{{}\begin{matrix}x\ge0\\x\ne\dfrac{9}{4}\end{matrix}\right.\)
2.
a,ĐK: \(x\ge\dfrac{1}{2}\)
PT\(\Leftrightarrow2x-1=25\Rightarrow x=13\left(tm\right)\)
b,ĐK: \(\forall x\in R\)
PT\(\Leftrightarrow3x+2=-27=>x=-\dfrac{29}{3}\) (tm)
3.
a,\(\sqrt{5}.\sqrt{1,2}.\sqrt{24}=\sqrt{120}.\sqrt{1,2}=12\)
b,\(\dfrac{\sqrt{4444}}{\sqrt{1111}}=\dfrac{\sqrt{4}.\sqrt{1111}}{\sqrt{1111}}=2\)
c,\(\sqrt{\dfrac{3}{5}}+\sqrt{\dfrac{5}{3}}-\dfrac{1}{2}\sqrt{60}=\dfrac{8}{\sqrt{15}}-\sqrt{15}=-\dfrac{7}{\sqrt{15}}\)
d,\(\sqrt{5+2\sqrt{6}}+\sqrt{5-2\sqrt{6}}=\sqrt{3}+\sqrt{2}+\sqrt{3}-\sqrt{2}=2\sqrt{3}\)

Gọi quãng dường từ HN đến đền H là x (km)
Thời gian lúc đi là: \(\frac{x}{30}\)
Thời gian lúc về là: \(\frac{x}{40}\)
Theo đề bài thì ta có:
\(\frac{x}{30}=\frac{x}{40}+\frac{36}{60}\)
\(\Leftrightarrow x=72\)

21 paid (loại 2)
22 will be (loại 1)
23 wouldn't have conquered (loại 3)
24 believed (loại 2)
25 would you choose (loại 2)
26 had scored (loại 3)
27 would certainlu accept ( loại 2)
28 had received (loại 3)
29 leave - calls (loại 0)
30 had (loại 2)
31 didn't drink (loại 2)
32 had turned on (loại 3)
33 had had (loại 3)
34 would have spoke (loại 3)
35 sends (loại 1)
36 wouldn't do (loại 2)
37 hadn't heard (loại 3)

a, A = \(\dfrac{3^{10}\times10+3^{10}\times6}{3^9\times2^4}\)
A = \(\dfrac{3^{10}\times\left(10+6\right)}{3^9\times2^4}\)
A = \(\dfrac{3^{10}\times16}{3^9\times16}\)
A = 3
c, C = \(\dfrac{36^{10}\times25^{15}}{30^8}\)
C = \(\dfrac{\left(6^2\right)^{10}.\left(5^2\right)^{15}}{30^8}\)
C = \(\dfrac{6^{20}.5^{30}}{6^8.5^8}\)
C = 612.522
25 not had a swim for 4 years
26 worked this kind of job
27 first time I have written a letter to a foreigner
28 visited France before
29 time someone has challenged his authority
30 attended the club before
31 is it since you last rode a bike
32 have you learnt English
33 since you last saw peter
34 have you swum in the pool
35 since both of you corresponded with each other
36 Mary gone shopping with my aunt