Ta có: \(\sqrt{9-\sqrt{17}}\cdot\sqrt{9+\sqrt{17}}\)
\(=\sqrt{\left(9-\sqrt{17}\right)\left(9+\sqrt{17}\right)}\)
\(=\sqrt{81-17}=\sqrt{64}=8\)
a) \(x^2-2x+3=\left(x-1\right)\sqrt{x^2-3x+3}\)
b) \(x+\sqrt{17-x^2}+x\sqrt{17-x^2}=9\)
Giải các phương trình sau:
1, \(\sqrt{x-2}-3\sqrt{x^2-4}=0\)
2, \(x+\sqrt{x-1}=13\)
3, \(\sqrt{x}-\sqrt{x-1}-\sqrt{x-4}+\sqrt{x+9}=0\)
4, \(\sqrt{x+3}=5-\sqrt{x-2}\)
5, \(\sqrt{16x+17}=8x-33\)
Cho x, y thoả mãn điều kiện \(3\left(x\sqrt{y-9}+y\sqrt{x-9}\right)=xy\) . Tính giá trị biểu thức:
\(S=\left(x-17\right)^{2018}+\left(y-19\right)^{2019}\)
Với a,b,c \(\ge0 \) thoả mãn a+b+c=1
TÌM GTNN CỦA \(Q=\sqrt{7a+9}+\sqrt{7b+9}+\sqrt{7c+9}\)
Tính :
a ) S= 5+55+555+...+55...5 ( 50 chữ số 5 )
b ) S= 75+755+7555+...+755...5 ( 50 chữ số 5 )
c ) \(S=\dfrac{1}{\sqrt{1}+\sqrt{3}}+\dfrac{1}{\sqrt{3}+\sqrt{5}}+\dfrac{1}{\sqrt{5}+\sqrt{7}}+...+\dfrac{1}{\sqrt{2017} +\sqrt{2019}}\)
d ) \(S=\dfrac{1}{\sqrt{3}+\sqrt{6}}+\dfrac{1}{\sqrt{6}+\sqrt{9}}+\dfrac{1}{\sqrt{9}+\sqrt{12}}+...+\dfrac{1}{\sqrt{2016}+\sqrt{2019}}\)
Bài 1:Tính
\(\left(\sqrt{18}+\sqrt{32}-\sqrt{50}\right)\cdot\sqrt{2}\)
1)Tìm max
\(17-x-y+xy+\sqrt{x}+\sqrt{y}\)
1. Tìm số tự nhiên n sao cho :
\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+..+\dfrac{1}{n.\left(n+1\right)}=\dfrac{2999}{3000}\)
2. Tính :
a ) \(S=2018.3+2018.4+2018.5+...+2018.2018\)
b ) \(\dfrac{1}{\sqrt{8}+\sqrt{10}}+\dfrac{1}{\sqrt{10}+\sqrt{12}}+\dfrac{1}{\sqrt{12}+\sqrt{14}}+...+\dfrac{1}{\sqrt{200}+\sqrt{202}}\)
c ) \(S=5.21^2+5.21^3+5.21^4+....+5.21^{2018}\)
d ) \(A=9+99+999+9999+...+9..9\)( 99 chữ số 9)
e ) 72+772+7772+...+77...72( 77 chữ số 7 )
2. Tính tổng :
a ) \(S=\dfrac{1}{3\sqrt{1}+3\sqrt{3}}+\dfrac{1}{3\sqrt{3}+3\sqrt{5}}+...+\dfrac{1}{3\sqrt{2017}+3\sqrt{2019}}\)
b ) S = \(\dfrac{1}{\sqrt{2.2}+\sqrt{2.3}}+\dfrac{1}{\sqrt{2.3}+\sqrt{2.4}}+\dfrac{1}{\sqrt{2.4}+\sqrt{2.5}}+...+\dfrac{1}{\sqrt{2.2018}+\sqrt{2.2019}}\)
\(\dfrac{9}{\sqrt{x-19}}+\dfrac{16}{\sqrt{y-5}}+\dfrac{25}{\sqrt{z-91}}=24-\sqrt{x-19}-\sqrt{y-5}-\sqrt{z-91}\)
