Chọn C

bạn giải thích ra đc ko

\(20=2^2\cdot5;12=2^2\cdot3\)

=>\(ƯCLN\left(20;12\right)=2^2=4\)

=>Số nhóm sẽ là ước của 4

mà số nhóm lớn hơn 1

nên số nhóm có thể là 2;4

=>Có 2 cách chia

cảm ơn nhìu nha! 

a) \(\dfrac{-14}{12}+0,65-\left(\dfrac{-7}{42}-0,35\right)\\ =\dfrac{-7}{6}+0,65+\dfrac{7}{42}+0,35\\ =\left(-\dfrac{7}{6}+\dfrac{7}{42}\right)+\left(0,65+0,35\right)\\ =\left(-\dfrac{7}{6}+\dfrac{1}{6}\right)+1\\ =\dfrac{-6}{6}+1=-1+1=0\)

b) \(\left(\dfrac{7}{8}-\dfrac{5}{2}+\dfrac{4}{7}\right)-\left(-\dfrac{3}{7}+1-\dfrac{13}{8}\right)\\ =\dfrac{7}{8}-\dfrac{5}{2}+\dfrac{4}{7}+\dfrac{3}{7}-1+\dfrac{13}{8}\\ =\left(\dfrac{7}{8}+\dfrac{13}{8}-\dfrac{5}{2}\right)+\left(\dfrac{4}{7}+\dfrac{3}{7}\right)-1\\ =\left(\dfrac{20}{8}-\dfrac{20}{8}\right)+\dfrac{7}{7}-1\\ =0+1-1=0\)

c) \(\dfrac{1}{2}-\dfrac{43}{101}+\left(-\dfrac{1}{3}\right)-\dfrac{1}{6}\\ =\dfrac{1}{2}-\dfrac{43}{101}-\dfrac{1}{3}-\dfrac{1}{6}\\ =\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{6}\right)-\dfrac{43}{101}\\ =\left(\dfrac{3}{6}-\dfrac{2}{6}-\dfrac{1}{6}\right)-\dfrac{43}{101}\\ =0-\dfrac{43}{101}=-\dfrac{43}{101}\)

a; - \(\dfrac{14}{12}\) + 0,65 - ( - \(\dfrac{7}{42}\) - 0,35)

  = - \(\dfrac{7}{6}\) + 0,65 + \(\dfrac{7}{42}\) + 0,35

= (- \(\dfrac{7}{6}\) + \(\dfrac{7}{42}\)) + (0,65 + 0,35)

= (-\(\dfrac{49}{42}\) + \(\dfrac{7}{42}\)) + 1

= - 1 + 1

= 0 

là d nha

d

\(\dfrac{1}{a^{150}}< \left(\dfrac{1}{5}\right)^{225}\\ \Rightarrow\left(\dfrac{1}{a}\right)^{150}< \left(\dfrac{1}{5}\right)^{225}\\ \Rightarrow\left[\left(\dfrac{1}{a}\right)^2\right]^{75}< \left[\left(\dfrac{1}{5}\right)^3\right]^{75}\\ \Rightarrow\left(\dfrac{1}{a}\right)^2< \left(\dfrac{1}{5}\right)^3\\ \Rightarrow\dfrac{1}{a^2}< \dfrac{1}{5^3}\\ \Rightarrow a^2>5^3\\ \Rightarrow a^2>125\)

Mà: a là số nguyên dương nhỏ nhất

Vậy: a = 12

giúp mik với ạ.

j

\(a,\left(-\dfrac{13}{7}-\dfrac{4}{9}\right)-\left(-\dfrac{10}{7}-\dfrac{4}{9}\right)\\ =-\dfrac{13}{7}-\dfrac{4}{9}+\dfrac{10}{7}+\dfrac{4}{9}\\ =-\dfrac{3}{7}.\)

a) $(-\frac{13}{7}-\frac49)-(-\frac{10}{7}-\frac49)$

$=-\frac{13}{7}-\frac49+\frac{10}{7}+\frac49$

$=(-\frac{13}{7}+\frac{10}{7})+(-\frac49+\frac49)$

$=\frac{-3}{7}$

\(\dfrac{2}{5}-x=2-\dfrac{3}{4}\\ \Rightarrow\dfrac{2}{5}-x=\dfrac{5}{4}\\ \Rightarrow x=-\dfrac{17}{20}.\)

$\frac25-x=2-\frac34$

$\frac25-x=\frac54$

$x=\frac25-\frac54$

$x=-\frac{17}{20}$