x + 10 = 40 x 2
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a, 10 x 7 = 70
20 x 4= 80
40 x 2 = 80
30 x 3= 90
b, 60:=2=30
70:7=10
90:3=30
40:2=20
a) 10 x 7=70
20 x 4=80
40 x 2=80
30 x 3=9-
b) 60:2=30
90:3=30
70:7=10
40:2=20
\(ĐK:2\le x\le10\)
\(PT\Leftrightarrow\left(\sqrt{x-2}-2\right)+\left(\sqrt{10-x}-2\right)=x^2-12x+36\\ \Leftrightarrow\dfrac{x-6}{\sqrt{x-2}+2}+\dfrac{6-x}{\sqrt{10-x}+2}-\left(x-6\right)^2=0\\ \Leftrightarrow\left(x-6\right)\left(\dfrac{1}{\sqrt{x-2}+2}-\dfrac{1}{\sqrt{10-x}+2}-x+6\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=6\left(tm\right)\\\dfrac{1}{\sqrt{x-2}+2}-\dfrac{1}{\sqrt{10-x}+2}-x+6=0\left(1\right)\end{matrix}\right.\)
Với \(x\le10\Leftrightarrow\left(1\right)\le\dfrac{1}{2\sqrt{2}+2}-\dfrac{1}{2}-10+6< 0\Leftrightarrow x\in\varnothing\)
Vậy \(x=6\)
a)
\(P=\dfrac{x^{10}-x^8+x^6-x^4+x^2-1}{x^4-1}\)
\(=\dfrac{x^8\left(x^2-1\right)+x^4\left(x^2-1\right)+\left(x^2-1\right)}{\left(x^2-1\right)\left(x^2+1\right)}\)
\(=\dfrac{\left(x^2-1\right)\left(x^8+x^4+1\right)}{\left(x^2-1\right)\left(x^2+1\right)}\)
\(=\dfrac{x^8+x^4+1}{x^2+1}\)
b)
\(Q=\dfrac{x^{40}+x^{30}+x^{20}+x^{10}+1}{x^{45}+x^{40}+x^{35}+...+x^{10}+x^5+1}\)
\(=\dfrac{x^{40}+x^{30}+x^{20}+x^{10}+1}{\left(x^{45}+x^{35}+...+x^5\right)+\left(x^{40}+x^{30}+...+1\right)}\)
\(=\dfrac{x^{40}+x^{30}+x^{20}+x^{10}+1}{x^5\left(x^{40}+x^{30}+...+1\right)+\left(x^{40}+x^{30}+...+1\right)}\)
\(=\dfrac{x^{40}+x^{30}+x^{20}+x^{10}+1}{\left(x^{40}+x^{30}+...+1\right)\left(x^5+1\right)}\)
\(=\dfrac{1}{\left(x^5+1\right)}\)
cái câu b dòng cuối mẫu số đóng mở ngoặc chi cho mệt ei =.=
\(a,\left(2\times x-40\right):10=-55\)
\(2\times x-40=-55\times10\)
\(2\times x-40=-550\)
\(2\times x=-550+40\)
\(2\times x=-510\)
\(x=-510:2\)
\(\Rightarrow x=-255\)
\(b,\left(2\times x+15\right):5=-40\)
\(2\times x+15=-40\times5\)
\(2\times x+15=-200\)
\(2\times x=-200-15\)
\(2\times x=-215\)
\(x=-215:2\)
\(\Rightarrow x=-\dfrac{215}{2}\)
\(c,\left(2\times x-72\right):8=25\)
\(2\times x-72=25\times8\)
\(2\times x-72=200\)
\(2\times x=200+72\)
\(2\times x=272\)
\(x=272:2\)
\(\Rightarrow x=136\)
x=70
k mình đi mình k bạn rồi lan hương ạ
x + 10 = 40 x 2
x + 10= 80
x = 80 - 10
x = 70
k mk mk k lại
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