Lời giải:
\(5\sqrt{2}+4\sqrt{5}-16=(\sqrt{50}-7)+(\sqrt{80}-9)\)
\(=\frac{1}{\sqrt{50}+7}-\frac{1}{\sqrt{80}+9}\)
Dễ thấy \(\sqrt{50}+7< \sqrt{80}+9\Rightarrow \frac{1}{\sqrt{50}+7}>\frac{1}{\sqrt{80}+9}\)
\(\Rightarrow 5\sqrt{2}+4\sqrt{5}-16=\frac{1}{\sqrt{50}+7}-\frac{1}{\sqrt{80}+9}>0\)
\(\Rightarrow 5\sqrt{2}+4\sqrt{5}>16\)
so sánh \(\sqrt{\sqrt{6+\sqrt{20}}}\) và \(\sqrt{1+\sqrt{6}}\)
Cho \(A=\sqrt{2017}-\sqrt{2016}\) ; \(B=\sqrt{2018}-\sqrt{2017}\). So sánh A và B.
CMR: \(\dfrac{4}{\sqrt{5}-1}+\dfrac{3}{\sqrt{5}-2}+\dfrac{16}{\sqrt{5}-3}=-5\)
So sánh 2 số: \(R=\dfrac{3+\sqrt{5}}{2\sqrt{2}+\sqrt{3+\sqrt{5}}}+\dfrac{3-\sqrt{5}}{2\sqrt{2}-\sqrt{3-\sqrt{5}}}\)
\(S=\dfrac{4+\sqrt{7}}{3\sqrt{2}+\sqrt{4+\sqrt{7}}}+\dfrac{4-\sqrt{7}}{2\sqrt{2}-\sqrt{3-\sqrt{5}}}\)
So sánh 2 số: \(R=\dfrac{3+\sqrt{5}}{2\sqrt{2}+\sqrt{3+\sqrt{5}}}+\dfrac{3-\sqrt{5}}{2\sqrt{2}-\sqrt{3-\sqrt{5}}}\)
\(S=\dfrac{4+\sqrt{7}}{3\sqrt{2}+\sqrt{4+\sqrt{7}}}+\dfrac{4-\sqrt{7}}{3\sqrt{2}-\sqrt{4-\sqrt{7}}}\)
Tìm x :
h/ \(\sqrt{x+5}-10=-4\)
i/ \(\sqrt{x-5}+2\sqrt{4x-20}-\frac{1}{3}\sqrt{9x-45}=12\)
j/ \(3\sqrt{2x}+\frac{1}{7}\sqrt{98x}-\sqrt{72x}+4=0\)
k/ \(\sqrt{4x^2-20}-\frac{1}{3}\sqrt{x^2-5}+\sqrt{\frac{9x^2-45}{16}}-\frac{1}{2}\sqrt{\frac{25x^2-125}{36}}=4\)
l/ \(\sqrt{4x+4}+\sqrt{9x+9}-\sqrt{x+1}=4\)
m/ \(\sqrt{16\left(x+1\right)}+\sqrt{4x+4}=16-\sqrt{x+1}+\sqrt{9x+9}\)
Giúp mk với nhé mn
Bài 1. (2,0 điểm) Thực hiện phép tính: n) 7/9 * sqrt(81) - 1/2 * sqrt(16) . c) (sqrt(8/3) - sqrt(24) + sqrt(50/3)) , sqrt 12 . » sqrt((sqrt(7) - 4) ^ 2) + sqrt(7) 1/(5 + 2sqrt(3)) + 1/(5 - 2sqrt(3))
rút gọn
a) \(\frac{7\sqrt{2}+2\sqrt{7}}{\sqrt{14}}-\frac{5}{\sqrt{7}+\sqrt{5}}\)
b) \(\frac{\sqrt{2}\left(3+\sqrt{5}\right)}{2\sqrt{2}+\sqrt{3+\sqrt{5}}}+\frac{\sqrt{2}\left(3-\sqrt{5}\right)}{2\sqrt{2}-\sqrt{3-\sqrt{5}}}\)
c) \(\sqrt[3]{16-8\sqrt{5}}+\sqrt[3]{16\text{ }+8\sqrt{5}}\)
helppp mee
Tính
a) \(\sqrt{\frac{9}{4}-\sqrt{2}}\)
b) \(\sqrt{\frac{129}{16}+\sqrt{2}}\)
c) \(\sqrt{\frac{289+4\sqrt{72}}{16}}\)
d) \(\sqrt{2}.\sqrt{7-3\sqrt{5}}\)