Question

[Phạm Trần Bình]

1 tìm x: a).  b).  

2 so sánh:  

giúp mình với mình cám ơn

Answer 1

[Nguyễn Lê Phước Thịnh]

1: 

a: \(1\dfrac{2}{3}-\dfrac{7}{12}x=\dfrac{-5}{24}\cdot\dfrac{8}{-15}\)

=>\(\dfrac{5}{3}-\dfrac{7}{12}x=\dfrac{5}{15}\cdot\dfrac{8}{24}=\dfrac{1}{9}\)

=>\(\dfrac{7}{12}x=\dfrac{5}{3}-\dfrac{1}{9}=\dfrac{14}{9}\)

=>\(x=\dfrac{14}{9}:\dfrac{7}{12}=\dfrac{14}{9}\cdot\dfrac{12}{7}=2\cdot\dfrac{4}{3}=\dfrac{8}{3}\)

b: \(\dfrac{25}{-30}=\dfrac{15}{x}\)

=>\(\dfrac{15}{x}=\dfrac{5}{-6}\)

=>\(x=\dfrac{15\cdot\left(-6\right)}{5}=-3\cdot6=-18\)

2:

\(\left(\dfrac{1}{32}\right)^7=\left[\left(\dfrac{1}{2}\right)^5\right]^7=\left(\dfrac{1}{2}\right)^{35}\)

\(\left(\dfrac{1}{16}\right)^9=\left[\left(\dfrac{1}{2}\right)^4\right]^9=\left(\dfrac{1}{2}\right)^{36}\)

mà 35<36 và 1/2<1

nên \(\left(\dfrac{1}{2}\right)^{35}>\left(\dfrac{1}{2}\right)^{36}\)

=>\(\left(\dfrac{1}{32}\right)^7>\left(\dfrac{1}{16}\right)^9\)