a)\(\sqrt{\frac{3a}{7}}-2\sqrt{\frac{7a}{3}}+\sqrt{21a}\) =\(\sqrt{\frac{3}{7}.\frac{1}{21}.21a}\) - \(2\sqrt{\frac{7}{3}.\frac{1}{21}.21a}\)+ \(\sqrt{21}\)
=\(\sqrt{\frac{1}{49}.21a}\) - \(2\sqrt{\frac{1}{9}.21a}\)+\(\sqrt{21}\)
=\(\sqrt{\frac{1}{49}}.\sqrt{21a}\) - \(2.\sqrt{\frac{1}{9}}.\sqrt{21a}\)+ \(\sqrt{21a}\)
=\(\frac{1}{7}\sqrt{21a}\) - \(\frac{2}{3}\sqrt{21a}\) + \(\sqrt{21a}\)
=\(\frac{-10}{21}\sqrt{21a}\)
b)
N=\(\sqrt{\frac{8x}{3}}\) - \(\sqrt{\frac{27x}{2}}\) + \(\sqrt{6x}\)
=\(\sqrt{\frac{8}{3}.\frac{1}{6}.6x}\) - \(\sqrt{\frac{27}{2}.\frac{1}{6}.6x}\)+ \(\sqrt{6x}\)
=\(\frac{2}{3}\sqrt{6x}-\frac{3}{2}.\sqrt{6x}+\sqrt{6x}\)
=\(\frac{1}{6}\sqrt{6x}\)
em lớp 8 nene làm theo cách hiểu thôi ạ
c)P=\(2\sqrt{\frac{8y}{5}}\) + \(\sqrt{\frac{45y}{2}}\) - \(\sqrt{10y}\)
=\(2\sqrt{\frac{8}{5}.\frac{1}{10}.10y}\) + \(\sqrt{\frac{45}{2}.\frac{1}{10}.10y}\) - \(\sqrt{10y}\)
=\(2\sqrt{\frac{4}{25}.10y}\) + \(\sqrt{\frac{9}{4}.10y}\) - \(\sqrt{10y}\)
=\(2\).\(\sqrt{\frac{4}{25}}\) \(.\sqrt{10y}\) + \(\sqrt{\frac{9}{4}}.\sqrt{10y}\) - \(\sqrt{10y}\)
=\(\frac{4}{5}\sqrt{10y}\) + \(\frac{3}{2}\sqrt{10y}\) - \(\sqrt{10y}\)
=\(\frac{13}{10}\sqrt{10y}\)
b, 1/6 căn 6x
c, 13/10 căn 10y
a, 10 căn a/21
a) M=-10/21 căn 21a
b) N=1/6 căn 6x
c) P=13/10 căn 10y
M=10√21a /21
N= √6x /6
P=33√10y /10
a. \(\dfrac{-10}{21}\sqrt{21a}\)
b. \(\dfrac{1}{6}\sqrt{6x}\)
c. \(\dfrac{13}{10}\sqrt{10y}\)
a) -10/21 can 21 a
b) 1/6 can 6x
c) 13/10 can 10y
a, M= căn 3a/7-2 căn 7a/3+21a
=1/7 căn 21+ 2/3căn 21a +căn 21
= - 10/21 căn 21a
b, N= căn 8x/3- căn x/2 +căn 6x
= 2/3 căn 6x - 2/3căn 6x+căn 6x
=1/6 căn 6x
c, P =2 căn 8y /5 + căn 45y/2 - căn 10y
= 4/5căn 10y + 3/2căn 10y - căn 10y
= 13/10căn 10y