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Bài này là bài của lớp 9 nha!! có chỗ nào ko hiểu ib
\(a,A=\sqrt{18}+\sqrt{50}-\frac{1}{2}\sqrt{98}.\)
\(=3\sqrt{2}+5\sqrt{2}-\frac{7}{2}\sqrt{2}\)
\(=\sqrt{2}\left(3+5-\frac{7}{2}\right)\)
\(=\frac{9}{2}\sqrt{2}\)
\(b,B=\left(2\sqrt{3}+7\right)\left(2\sqrt{3}-7\right)\)
\(=2^2\sqrt{3^2}-7^2\)
\(=12-49=-37\)
a )
\(A=\sqrt{18}+\sqrt{50}-\frac{1}{2}\sqrt{98}\)
\(A=3\sqrt{2}+5\sqrt{2}-\frac{7}{2}\sqrt{2}\)
\(A=(3+5-\frac{7}{2})\sqrt{2}\)
\(A=\frac{9}{2}\sqrt{2}=\frac{9\sqrt{2}}{2}\)
b)
\(B=\left(2\sqrt{3}+7\right)\left(2\sqrt{3}-7\right)=\left(2\sqrt{3}\right)^2-7^2=12-49=-37\)
a: \(=\sqrt{7}+1\)
b: \(=\sqrt{5}+\sqrt{2}\)
c: \(=\sqrt{5}-\sqrt{3}\)
d: \(=2\sqrt{3}-\sqrt{7}\)
a) \(\sqrt{\left(-5\right)^2}+\sqrt{5^2}-\sqrt{\left(-3\right)^2}-\sqrt{3^2}-\left(\sqrt{7}\right)^2=\sqrt{25}+\sqrt{25}-\sqrt{9}-\sqrt{9}\)
\(=5+5-3-3\)
\(=4\)
c) \(\sqrt{\left(-10\right)^2}+10.\left(-\sqrt{5}\right)^2=\sqrt{100}+10.5\)
\(=10+10.5\)
\(=10+50\)
\(=60\)
Học tốt nha^^
a, \(-\frac{187}{70}\)
b,\(\frac{27}{70}\)
c,\(\frac{53}{14}\)
d,\(\frac{27}{4}\)
e,1
f,\(\frac{23}{4}\)
g,-1
i,6
k,315
l,\(\frac{9}{2}\)
a)\(\sqrt{\dfrac{3^2}{7^2}}=\sqrt{\dfrac{9}{49}}=\sqrt{\dfrac{3}{7}}\)
b)\(\dfrac{\sqrt{3^2}+\sqrt{39^2}}{\sqrt{7^2}+\sqrt{91^2}}=\dfrac{\sqrt{9}+\sqrt{1521}}{\sqrt{49}+\sqrt{8281}}=\dfrac{3+39}{7+91}=\dfrac{42}{98}\)
c)Tương tự câu b, ta đc:
\(\dfrac{\sqrt{3^2}-\sqrt{39^2}}{\sqrt{7^2}-\sqrt{91^2}}=\dfrac{3-39}{7-91}=\dfrac{-36}{86}=\dfrac{3}{7}\)
d)Tương tự câu a, ta đc:
\(\dfrac{\sqrt{39^2}}{\sqrt{91^2}}=\dfrac{39}{91}\)
Chúc Bạn Học Tốt!!!
a) \(\sqrt{\dfrac{3^2}{7^2}}=\sqrt{\left(\dfrac{3}{7}\right)^2}=\left|\dfrac{3}{7}\right|=\dfrac{3}{7}\)
b) \(\dfrac{\sqrt{3}^2+\sqrt{39}^2}{\sqrt{7}^2+\sqrt{91}^2}=\dfrac{\left|3\right|+\left|39\right|}{\left|7\right|+\left|91\right|}=\dfrac{3+39}{7+91}=\dfrac{42}{98}=\dfrac{3}{7}\)
c) \(\dfrac{\sqrt{3}^2-\sqrt{39}^2}{\sqrt{7}^2-\sqrt{91}^2}=\dfrac{\left|3\right|- \left|39\right|}{\left|7\right|-\left|91\right|}=\dfrac{3-39}{7-91}=\dfrac{-36}{-84}=\dfrac{3}{7}\)
d) \(\sqrt{\dfrac{39^2}{91^2}}=\sqrt{\left(\dfrac{39}{91}\right)^2}=\left|\dfrac{39}{91}\right|=\dfrac{39}{91}=\dfrac{3}{7}\)
a) 1,(3) = 10+(3-1)/9 =12/9 = 4/3
...................
b) chẳng hiu dau bai
c) = 5 ; =7 ; = 10