Bài 5:
a: (7x-15):3=9
=>\(7x-15=3\cdot9=27\)
=>7x=15+27=42
=>\(x=\dfrac{42}{7}=6\)
d: \(71+\left(x-16:2^2\right)=75\)
=>71+x-4=75
=>x+67=75
=>x=75-67=8
g: \(\left(5+x\right)^2-36=0\)
=>\(\left(x+5\right)^2=36\)
=>\(\left[{}\begin{matrix}x+5=6\\x+5=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=6-5=1\\x=-6-5=-11\end{matrix}\right.\)
j: \(\left(3x+2\right)^3=11\cdot121\)
=>\(\left(3x+2\right)^3=11\cdot11^2=11^3\)
=>3x+2=11
=>3x=9
=>x=3
b: 70-5(x-3)=45
=>5(x-3)=70-45=25
=>\(x-3=\dfrac{25}{5}=5\)
=>x=5+3=8
e: \(\left[43-\left(56-x\right)\right]\cdot12=384\)
=>\(\left[43-56+x\right]=\dfrac{384}{12}=32\)
=>x-13=32
=>x=32+13=45
h: \(\left(7x-11\right)^3=2^5\cdot5^2+200\)
=>\(\left(7x-11\right)^3=32\cdot25+200=1000=10^3\)
=>7x-11=10
=>7x=10+11=21
=>\(x=\dfrac{21}{7}=3\)
k: \(720:\left[41-\left(2x-5\right)\right]=2^3\cdot5\)
=>\(720:\left[41-2x+5\right]=8\cdot5=40\)
=>46-2x=18
=>2x=46-18=28
=>\(x=\dfrac{28}{2}=14\)
c: \(71+5\left(x-29\right)=4\cdot7^2\)
=>\(5\cdot\left(x-29\right)+71=4\cdot49=196\)
=>5(x-29)=196-71=125
=>x-29=25
=>x=25+29=54
f: \(3^x\cdot2+15=33\)
=>\(3^x\cdot2=33-15=18\)
=>\(3^x=\dfrac{18}{2}=9=3^2\)
=>x=2
i: \(3^x+4^2=\left(8-3\right)^2\)
=>\(3^x+16=5^2=25\)
=>\(3^x=25-16=9=3^2\)
=>x=2
l: \(2024^{x-2023}+3=\left(7-5\right)^2\)
=>\(2024^{x-2023}+3=2^2=4\)
=>\(2024^{x-2023}=1=2024^0\)
=>x-2023=0
=>x=2023
Bài 7:
Số chỗ ở mỗi khoang là:
\(11\cdot8=88\left(chỗ\right)\)
\(\dfrac{980}{88}=11\left(dư12\right)\)
=>Cần ít nhất là 11+1=12 toa để chở hết khách
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