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a, |2x-1| = |x+7|
+, Với x < -7
=> 1-2x = -x-7
=> x = 8 (ko tm)
+, Với -7 < = x < = 1/2
=> 1-2x = x+7
=> x = -2 (tm)
+, Với x > 1/2
=> 2x-1 = x+7
=> 8 (tm)
Vậy .............
b, |x+4|+|x-7| = 9
Có : |x+4|+|x-7| = |x+4|+|7-x| >= |x+4+7-x| = 11
=> ko tồn tại x tm bài toán
Tk mk nha
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\(\left(x-1\right)^4=81\)
\(\Rightarrow\left(x-1\right)^4=\left(\pm3\right)^4\)
\(\Rightarrow\orbr{\begin{cases}x-1=3\\x-1=-3\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=4\\x=-2\end{cases}}\)
vậy___
a - (- 351) - (621 + 451 - 821)
= a + 351 - 621 - 451 + 821
= a - (451 - 351) + (821 - 621)
= a - 100 + 100
= a - 0
= a
1,\(\left(x-1\right)^4=81\)
\(\Rightarrow\left(x-1\right)^4=\orbr{\begin{cases}3^4\\\left(-3\right)^4\end{cases}}\)
\(\Rightarrow x-1=\orbr{\begin{cases}3\\-3\end{cases}}\)
\(\Rightarrow x=\orbr{\begin{cases}4\\-2\end{cases}}\)
2,\(a-\left(-351\right)-\left(621+451-821\right)\)
\(=a+351-251\)
\(=a+100\)
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a) Ta có: \(\dfrac{21}{25}\cdot\dfrac{11}{9}\cdot\dfrac{5}{7}\)
\(=\dfrac{21\cdot11\cdot5}{25\cdot9\cdot7}\)
\(=\dfrac{3\cdot7\cdot11\cdot5}{5\cdot5\cdot3\cdot3\cdot7}\)
\(=\dfrac{11}{5\cdot3}=\dfrac{11}{15}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có:
A=\(\frac{3^{10}.11+3^8.45}{3^9.16}\)
A=\(\frac{3^{10}.11+3^{10}.5}{3^9.16}\)
A=\(\frac{3^{10}.\left(11+5\right)}{3^9.16}\)
A=\(\frac{3^{10}.16}{3^9.16}\)
A=3
Hok tốt
\(\frac{3^{10}.11+3^8.45}{3^9.16}\)
=\(\frac{59049.11+6561.45}{19683.16}\)
=\(\frac{649539+295245}{314928}\)
=\(\frac{944784}{314928}\)
=3
\(\Rightarrow]\) K CHO MÌNH NHA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!PLEASE