81 x 4 =??????
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\(4^{x-5}=16\)
\(4^{x-5}=4^2\)
\(x-5=2\)
\(x=2+5\)
\(x=7\)
\(45-2^{x-1}=29\)
\(2^{x-1}=16\)
\(2^{x-1}=2^4\)
\(x-1=4\)
\(x=5\)
\(\left(2+x\right)^2=144\)
\(\left(2+x\right)^2=12^2\)
\(2+x=12\)
\(x=12-2\)
\(x=10\)
\(\left(x-5\right)^2=81\)
\(\left(x-5\right)^2=9^2\)
\(x-5=9\)
\(x=14\)
\(\left(13-x\right)^4=81\)
\(\left(13-x\right)^4=3^4\)
\(13-x=3\)
\(x=13-3\)
\(x=10\)
\(...4^{x-5}=4^2\Rightarrow x-5=2\Rightarrow x=7\)
\(...2^{x-1}=45-29=16\Rightarrow2^{x-1}=2^4\Rightarrow x-1=4\Rightarrow x=5\)
\(...\Rightarrow\left(2+x\right)^2=12^2\Rightarrow\left[{}\begin{matrix}2+x=12\\2+x=-12\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=10\\x=-14\end{matrix}\right.\)
\(...\Rightarrow\left(x-5\right)^2=9^2\Rightarrow\left[{}\begin{matrix}x-5=3\\x-5=-3\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=8\\x=2\end{matrix}\right.\)
\(...\Rightarrow\left(13-x\right)^4=3^4\Rightarrow\left[{}\begin{matrix}13-x=3\\13-x=-3\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=10\\x=16\end{matrix}\right.\)
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Bài 2:
x=13 nên x+1=14
\(f\left(x\right)=x^{14}-x^{13}\left(x+1\right)+x^{12}\left(x+1\right)-...+x^2\left(x+1\right)-x\left(x+1\right)+14\)
\(=x^{14}-x^{14}-x^{13}+x^{13}-...+x^3+x^2-x^2-x+14\)
=14-x=1
x=13 nên x+1=14
f(x)=x14−x13(x+1)+x12(x+1)−...+x2(x+1)−x(x+1)+14f(x)=x14−x13(x+1)+x12(x+1)−...+x2(x+1)−x(x+1)+14
=x14−x14−x13+x13−...+x3+x2−x2−x+14=x14−x14−x13+x13−...+x3+x2−x2−x+14
=14-x=1
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a,
18:3=6 và (18.4):(3.4)=72:12=6
=>18:3=(18.4):(3.4)
b,81:9=9 và (81:3):(9:3)=27:3=9
=>81:9=(81:3):(9:3)
K mình nhé!
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81 x 4 = 324
81 x4 =324