Rút gọn biểu thức :
a) \(A=\sqrt{4+\sqrt{7}}+\sqrt{4-\sqrt{7}}\)
b) \(B=\frac{2+\sqrt{6}+\sqrt{10}+\sqrt{2}+\sqrt{3}+\sqrt{5}}{\sqrt{8}+\sqrt{12}+\sqrt{20}}.\frac{\sqrt{2}-1}{3}\)
bài 1:
a) Rút gọn biểu thức : \(\sqrt{\frac{2\sqrt{10}+\sqrt{30}-2\sqrt{2}-\sqrt{6}}{2\sqrt{10}-2\sqrt{2}}}:\frac{2}{\sqrt{3}-1}\)
b) giải phương trình sau: \(\sqrt{\frac{1}{4}x^2+x+1}-\sqrt{6-2\sqrt{5}}=0\)
c) tính A= \(\left(\sqrt{4+\sqrt{7}}-\sqrt{4-\sqrt{7}}\right)^3\)
d) rút gọn biểu thức B= \(\sqrt{3-2\sqrt{2}}+\sqrt{3+2\sqrt{2}}\)
1) Rút gọn biểu thức:
a) \(\frac{1}{7+4\sqrt{3}}+\frac{1}{7-4\sqrt{3}}\)
b) \(\frac{15}{\sqrt{6}+1}+\frac{4}{\sqrt{6}-2}-\frac{12}{3-\sqrt{6}}-\sqrt{6}\)
c) \(\frac{5}{4-\sqrt{11}}+\frac{1}{3+\sqrt{7}}-\frac{6}{\sqrt{7}-2}-\frac{\sqrt{7}-5}{2}\)
d) \(\frac{4}{\sqrt{5}-\sqrt{2}}+\frac{3}{\sqrt{5}-2}-\frac{2}{\sqrt{3}-2}+\frac{\sqrt{3}-1}{6}\)
a) \(=\frac{7-4\sqrt{3}+7+4\sqrt{3}}{\left(7+4\sqrt{3}\right)\left(7-4\sqrt{3}\right)}=\frac{14}{49-48}=14\)
b) \(=\frac{15\left(\sqrt{6}-1\right)}{\left(\sqrt{6}+1\right)\left(\sqrt{6}-1\right)}-\frac{5\sqrt{6}}{5}+\frac{4\sqrt{3}-12\sqrt{2}}{\sqrt{6}\left(\sqrt{3}-\sqrt{2}\right)}\)
Rút gọn biểu thức:
a,\(\frac{3+\sqrt{5}}{\sqrt{10}+\sqrt{3+\sqrt{5}}}-\frac{3-\sqrt{5}}{\sqrt{10}+\sqrt{3-\sqrt{5}}}\)
\(b,\sqrt{4+\sqrt{7}}-\sqrt{4-\sqrt{7}}-\sqrt{2}\)
rút gọn các biểu thức
a/ A=\(\sqrt{7+2\sqrt{6}}+\sqrt{7-2\sqrt{6}}-2\sqrt{6}\)
b/ B= \(\sqrt{7+2\sqrt{10}}-\sqrt{7+2\sqrt{10}}-\sqrt{8}\)
c/ C=\(\sqrt{14+4\sqrt{6}}-\sqrt{14-4\sqrt{6}}\)
d/ D=\(\sqrt{3+\sqrt{5}}-\sqrt{3-\sqrt{5}}\)
e/ E=\(\frac{\sqrt{2-\sqrt{3}}}{\sqrt{2}}\)
f/ F=\(\frac{\sqrt{x-\sqrt{2x-1}}}{\sqrt{2}}với\frac{1}{2}\le x< 1\)
bài 1) rút gọn
1) 5√\(\frac{1}{5}\) 2)\(\frac{12}{5}\)√\(\frac{5}{4}\) 3)\(\frac{30}{5\sqrt{6}}\) 4) \(\frac{20}{2\sqrt{5}}\) 5)\(\frac{2-\sqrt{2}}{\sqrt{2}}\) 6) \(\frac{11+\sqrt{11}}{1+\sqrt{ }11}\) 7) \(\frac{\sqrt{21-\sqrt{7}}}{1-\sqrt{3}}\) 8)\(\frac{\sqrt{2+\sqrt{3}}}{2+\sqrt{6}}\) 9)\(\frac{\sqrt{10-\sqrt{2}}}{\sqrt{5-}1}\) 10)\(\frac{2\sqrt{3}-3\sqrt{2}}{\sqrt{3}-\sqrt[]{2}}\)
bài 2) với các biểu thức đã cho là có nghĩa và rút gọn
1)\(\frac{x-\sqrt{x}}{\sqrt{x}-1}\) 2)\(\frac{x\sqrt{x}-2x}{2-\sqrt{x}}\) 3) \(\frac{x\sqrt{y}-y\sqrt{x}}{\sqrt{x}-\sqrt{y}}\) 4) \(\frac{a\sqrt{b}-\sqrt{a}}{\sqrt{b}-b\sqrt{a}}\) 5) \(\frac{a-1}{\sqrt{a}+1}\) 6) \(\frac{4-x}{2\sqrt{x}-x}\) 7)\(\frac{a+1+2\sqrt{a}}{1+\sqrt{a}}\) 8)\(\frac{3\sqrt{x}-x}{3+2\sqrt{3x}-x}\) 9)\(\frac{y+12-4\sqrt{3y}}{y-12}\) 10)\(\frac{4\sqrt{x}-x-4}{x-4}\) 11)\(\frac{x+y-2\sqrt{xy}}{x\sqrt{y}-y\sqrt{x}}\)
ĐỀ KIỂM TRA 1 TIẾT TỔNG HỢP
1. Tính \(\sqrt{6+2\sqrt{8\sqrt{2}-9}}-\sqrt{7-\sqrt{2}}\) (căn 7 - căn căn 2 ) (1đ)
2. Rút gọn: \(\frac{2\sqrt{2}+2\sqrt{3}+4}{\sqrt{2}+\sqrt{3}+\sqrt{6}+\sqrt{12}+5}\)(1đ)
3. Rút gọn \(\sqrt{\frac{27\left(m^2-6m+9\right)}{48}}\)với m < 3 (1đ)
4. Tìm GTNN của biểu thức và x tương ứng: \(M=\sqrt{16x^2-8x+2}\)(0,5đ)
5. Cho biểu thức: (2,5đ)
\(A=\left(\frac{1}{x-\sqrt{x}}+\frac{1}{\sqrt{x}-1}\right):\frac{\sqrt{x}+1}{x-2\sqrt{x}+1}\)với x >0, x khác 1
Hãy tìm x để A có nghĩa rồi:
a/ Rút gọn A
b/ Tìm x biết A =-1
6. Giai phương trình \(\sqrt{16x-32}-\sqrt{4x-8}+\sqrt{9x-18}=1\)(0,5đ)
7. Giai phương trình \(\sqrt{x^2+2x+6}=x+2\)(0,5đ)
8. Thực hiện phép tính: \(B=\sqrt{5}\left(1-\sqrt{5}\right)+\sqrt{\sqrt{5}+1}.\sqrt{\sqrt{5}-1}\)(0,5đ)
9. Rút gọn biểu thức E = \(\sqrt{\frac{b}{a}}+ab\sqrt{\frac{1}{ab}}-\frac{b}{a}.\sqrt{\frac{a}{b}}\)(0,5đ)
10. Giai phương trình sau: \(\sqrt{4x-12}-\sqrt{25x-75}-\sqrt{x-3}=4-\sqrt{16x-48}\)(0,5đ)
11. Cho biểu thức: \(F=\left(\frac{1}{\sqrt{a}-1}-\frac{1}{\sqrt{a}}\right):\left(\frac{\sqrt{a}-1}{\sqrt{a}+2}-\frac{\sqrt{a}+2}{\sqrt{a}-1}\right)\)với a >0, a khác 1
a/ Rút gọn F
b/ Tìm giá trị của a để trị F = -F
Rút gọn các biểu thức
\(B=\frac{9\sqrt{5}+3\sqrt{27}}{\sqrt{5}+\sqrt{3}} \)
\(C=\frac{\sqrt{2}+\sqrt{3}+\sqrt{6}+\sqrt{8}+4}{\sqrt{2}+\sqrt{3}+\sqrt{4}}\)
\(D=\frac{3\sqrt{8}-2\sqrt{12}+20}{3\sqrt{18}-2\sqrt{27}+\sqrt{45}}\)
\(B=\frac{9\sqrt{5}+3\sqrt{27}}{\sqrt{5}+\sqrt{3}}=\frac{9\sqrt{5}+9\sqrt{3}}{\sqrt{5}+\sqrt{3}}=\frac{9\left(\sqrt{5}+\sqrt{3}\right)}{\sqrt{5}+\sqrt{3}}=9\)
\(C=\frac{\sqrt{2}+\sqrt{3}+\sqrt{6}+\sqrt{8}+4}{\sqrt{2}+\sqrt{3}+\sqrt{4}}\)
\(=\frac{\sqrt{2}+\sqrt{3}+\sqrt{6}+\sqrt{8}+\sqrt{4}+\sqrt{4}}{\sqrt{2}+\sqrt{3}+\sqrt{4}}\)
\(=\frac{\left(\sqrt{2}+\sqrt{3}+\sqrt{4}\right)+\sqrt{2}.\left(\sqrt{2}+\sqrt{3}+\sqrt{4}\right)}{\sqrt{2}+\sqrt{3}+\sqrt{4}}\)
\(=\frac{\left(\sqrt{2}+\sqrt{3}+\sqrt{4}\right)\left(\sqrt{2}+1\right)}{\sqrt{2}+\sqrt{3}+\sqrt{4}}=\sqrt{2}+1\)
mik chỉnh lại đề
\(D=\frac{3\sqrt{8}-2\sqrt{12}+\sqrt{20}}{3\sqrt{18}-2\sqrt{27}+\sqrt{45}}=\frac{6\sqrt{2}-4\sqrt{3}+2\sqrt{5}}{9\sqrt{2}-6\sqrt{3}+3\sqrt{5}}\)
\(=\frac{2\left(3\sqrt{2}-2\sqrt{3}+\sqrt{5}\right)}{3\left(3\sqrt{2}-2\sqrt{3}+\sqrt{5}\right)}=\frac{2}{3}\)
Rút gọn biểu thức.
a)\(\sqrt{3+2\sqrt{2}-\sqrt{3-2\sqrt{2}}}\). c)\(\sqrt{5-2\sqrt{6}}+\sqrt{7+2\sqrt{10}}\)
b)\(\sqrt{7-4\sqrt{3}+\sqrt{12+6\sqrt{3}}}\) d)\(\frac{\sqrt{8-2\sqrt{12}}}{\sqrt{3}-1}\)-\(\sqrt{8}\)
a) Ta có: \(\sqrt{3+2\sqrt{2}-\sqrt{3-2\sqrt{2}}}\)
\(=\sqrt{3+2\sqrt{2}-\sqrt{2-2\cdot\sqrt{2}\cdot1+1}}\)
\(=\sqrt{3+2\sqrt{2}-\sqrt{\left(\sqrt{2}-1\right)^2}}\)
\(=\sqrt{3+2\sqrt{2}-\left|\sqrt{2}-1\right|}\)
\(=\sqrt{3+2\sqrt{2}-\left(\sqrt{2}-1\right)}\)
\(=\sqrt{3+2\sqrt{2}-\sqrt{2}+1}\)
\(=\sqrt{4+\sqrt{2}}\)
b) Ta có: \(\sqrt{7-4\sqrt{3}+\sqrt{12+6\sqrt{3}}}\)
\(=\sqrt{7-4\sqrt{3}+\sqrt{9+2\cdot3\cdot\sqrt{3}\cdot3}}\)
\(=\sqrt{7-4\sqrt{3}+\sqrt{\left(3+\sqrt{3}\right)^2}}\)
\(=\sqrt{7-4\sqrt{3}+\left|3+\sqrt{3}\right|}\)
\(=\sqrt{7-4\sqrt{3}+3+\sqrt{3}}\)
\(=\sqrt{10-3\sqrt{3}}\)
c) Ta có: \(\sqrt{5-2\sqrt{6}}+\sqrt{7+2\sqrt{10}}\)
\(=\sqrt{3-2\cdot\sqrt{3}\cdot\sqrt{2}+2}+\sqrt{2+2\cdot\sqrt{2}\cdot\sqrt{5}+5}\)
\(=\sqrt{\left(\sqrt{3}-\sqrt{2}\right)^2}+\sqrt{\left(\sqrt{2}+\sqrt{5}\right)^2}\)
\(=\left|\sqrt{3}-\sqrt{2}\right|+\left|\sqrt{2}+\sqrt{5}\right|\)
\(=\sqrt{3}-\sqrt{2}+\sqrt{2}+\sqrt{5}\)
\(=\sqrt{3}+\sqrt{5}\)
d) Ta có: \(\frac{\sqrt{8-2\sqrt{12}}}{\sqrt{3}-1}-\sqrt{8}\)
\(=\frac{\sqrt{6-2\cdot\sqrt{6}\cdot\sqrt{2}+2}}{\sqrt{3}-1}-\sqrt{8}\)
\(=\frac{\sqrt{\left(\sqrt{6}-\sqrt{2}\right)^2}}{\sqrt{3}-1}-\sqrt{8}\)
\(=\frac{\left|\sqrt{6}-\sqrt{2}\right|}{\sqrt{3}-1}-2\sqrt{2}\)
\(=\frac{\sqrt{6}-\sqrt{2}}{\sqrt{3}-1}-2\sqrt{2}\)
\(=\frac{2\left(\sqrt{3}-1\right)}{\sqrt{3}-1}-2\sqrt{2}\)
\(=2-2\sqrt{2}\)
Rút gọn các biểu thức sau:
9, A = \(\sqrt{4+\sqrt{15}}-\sqrt{7-3\sqrt{5}}\)
10, A = \(\sqrt{2+\sqrt{3}}+\sqrt{2-\sqrt{3}}\)
11, A = \(\text{}\text{}\text{}\sqrt{12-3\sqrt{7}}-\sqrt{12+3\sqrt{7}}\)
12, A = \(\left(3\sqrt{2}+\sqrt{6}\right)\sqrt{6-3\sqrt{3}}\)
13, A = \(\sqrt{9-4\sqrt{5}}-\sqrt{14-6\sqrt{5}}\)
9: \(A=\dfrac{\sqrt{8+2\sqrt{15}}-\sqrt{14-6\sqrt{5}}}{\sqrt{2}}\)
\(=\dfrac{\sqrt{5}+\sqrt{3}-3+\sqrt{5}}{\sqrt{2}}=\dfrac{2\sqrt{10}+\sqrt{6}-3\sqrt{2}}{2}\)
10: \(A=\dfrac{\sqrt{4+2\sqrt{3}}+\sqrt{4-2\sqrt{3}}}{\sqrt{2}}\)
\(=\dfrac{\sqrt{3}+1+\sqrt{3}-1}{\sqrt{2}}=\dfrac{2\sqrt{3}}{\sqrt{2}}=\sqrt{6}\)
11: \(A=\dfrac{\sqrt{24-6\sqrt{7}}-\sqrt{24+6\sqrt{7}}}{\sqrt{2}}\)
\(=\dfrac{\sqrt{21}-\sqrt{3}-\sqrt{21}-\sqrt{3}}{\sqrt{2}}=-\dfrac{2\sqrt{3}}{\sqrt{2}}=-\sqrt{6}\)
12: \(B=\left(3+\sqrt{3}\right)\sqrt{12-6\sqrt{3}}\)
\(=\left(3+\sqrt{3}\right)\left(3-\sqrt{3}\right)\)
=9-3=6
13: \(A=\sqrt{5}-2-\left(3-\sqrt{5}\right)\)
\(=\sqrt{5}-2-3+\sqrt{5}=2\sqrt{5}-5\)