Chương I - Căn bậc hai. Căn bậc ba

NL

So sánh:

a) \(\dfrac{1}{4}\sqrt{8}\)\(\dfrac{2}{3}\sqrt{12}\)

b) \(\dfrac{5}{2}\sqrt{\dfrac{1}{6}}\)\(6\sqrt{\dfrac{1}{35}}\)

c) \(\dfrac{1}{6}\sqrt{18}\)\(\dfrac{1}{2}\sqrt{2}\)

TN
18 tháng 8 2018 lúc 10:00

So Sánh

a.\(\dfrac{1}{4}\sqrt{8}\)\(\dfrac{2}{3}\sqrt{12}\)

Có:\(\dfrac{1}{4}\sqrt{8}\)\(\dfrac{2}{3}\sqrt{12}\)

= \(\dfrac{1}{4}.2\sqrt{2}\)\(\dfrac{2}{3}.2\sqrt{3}\)

=\(\dfrac{\sqrt{2}}{2}\)\(\dfrac{4\sqrt{3}}{3}\)

=> \(\dfrac{1}{4}\sqrt{8}< \dfrac{2}{3}\sqrt{12}\)

b. \(\dfrac{5}{2}\sqrt{\dfrac{1}{6}}\)\(6\sqrt{\dfrac{1}{35}}\)

\(\dfrac{5}{2}\sqrt{\dfrac{1}{6}}\)\(6\sqrt{\dfrac{1}{35}}\)

=\(\dfrac{5}{2}.\dfrac{\sqrt{6}}{6}\)\(6.\dfrac{\sqrt{35}}{35}\)

=\(\dfrac{5\sqrt{6}}{12}\)\(\dfrac{6\sqrt{35}}{35}\)

=> \(\dfrac{5}{2}\sqrt{\dfrac{1}{6}}>6\sqrt{\dfrac{1}{35}}\)

c. \(\dfrac{1}{6}\sqrt{18}\)\(\dfrac{1}{2}\sqrt{2}\)

=\(\dfrac{1}{6}.3\sqrt{2}\)\(\dfrac{1}{2}\sqrt{2}\)

=\(\dfrac{\sqrt{2}}{2}\)\(\dfrac{\sqrt{2}}{2}\)

=> \(\dfrac{1}{6}\sqrt{18}=\dfrac{1}{2}\sqrt{2}\)

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