Tìm x biết:
a. \(\left\{\left[\left(3x-7\right).2-3\right]-10\right\}:9=9\)
b. \(\left(7x-11\right)^3=2^5.5^2+200\)
Hướng dẫn giải
a. \(\left\{\left[\left(3x-7\right).2-3\right]-10\right\}:9=9\)
\(\Rightarrow\left[\left(3x-7\right).2-3\right]-10=81\)
\(\Rightarrow\left(3x-7\right).2-3=91\Rightarrow2\left(3x-7\right)=94\Rightarrow3x-7=47\)
\(\Rightarrow3x=54\Rightarrow x=18.\)
b. \(\left(7x-11\right)^3=2^5.5^2+200\)
\(\Rightarrow\left(7x-11\right)^3=800+200\)
\(\Rightarrow\left(7x-11\right)^3=1000=\left(10\right)^3\)
\(\Rightarrow7x-11=10\Rightarrow7x=21\Rightarrow x=3.\)
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