Question

Tính giá trị của các biểu thức sau :

a/ \(A=\dfrac{1}{\sqrt{25}}+\dfrac{\sqrt{49}}{\sqrt{36}}-\dfrac{2}{\sqrt{100}}\)

b/ \(B=\sqrt{\dfrac{0,01}{1,21}}+3.\dfrac{2}{\sqrt{10^2}+2^2+40}-\dfrac{3}{4}\)

Answer 1

a) \(A=\dfrac{1}{\sqrt{25}}+\dfrac{\sqrt{49}}{\sqrt{36}}-\dfrac{2}{\sqrt{100}}.\)

\(=\dfrac{1}{5}+\dfrac{7}{6}-\dfrac{1}{5}.\)

\(=\left(\dfrac{1}{5}-\dfrac{1}{5}\right)+\dfrac{7}{6}.\)

\(=0+\dfrac{7}{6}=\dfrac{7}{6}.\)

Vậy \(A=\dfrac{7}{6}.\)

b) \(B=\sqrt{\dfrac{0,01}{1,21}}+3.\dfrac{2}{\sqrt{10^2}+2^2+40}-\dfrac{3}{4}.\)

\(=\dfrac{1}{11}+3.\dfrac{2}{10+4+40}-\dfrac{3}{4}.\)

\(=\dfrac{1}{11}+3.\dfrac{1}{37}-\dfrac{3}{4}.\)

\(=\dfrac{1}{11}+\dfrac{1}{9}-\dfrac{3}{4}.\)

\(=\dfrac{36}{396}+\dfrac{44}{396}-\dfrac{297}{296}.\)

\(=-\dfrac{217}{396}.\)

Vậy \(B=-\dfrac{217}{396}.\)