a) Ta có: 128 = (3.4)8 = 38.48 = 38.(22)8 = 38.216
812 = (23)12 = 236 = 220.216 = (22)10.216 = 410.216
Vì 38.216 < 410.216
=> 128 < 812
b) (-5)39 = -539 = -(53)13 = -12513
(-2)91 = -291 = -(27)13 = -12813
Vì 12513 < 12813
=> -12513 > -12813
=> (-5)39 > (-2)91
So sánh các cặp số sau :
a) \(12^8và8^{12}\)
b) \(\left(-5\right)^{39}và\left(-2\right)^{91}\)
HELP ME 
Tính:
a)\(\left\{\left[\left(6,2:0,31-\frac{5}{6}.0,9\right).0,2+0,15\right]:0,2\right\}:\left[\left(2+1\frac{4}{11}:0,1\right).\frac{1}{33}\right]\)
b)\(0,4\left(3\right)+0,6\left(2\right)-2\frac{1}{2}.\left[\left(\frac{1}{2}+\frac{1}{3}:0,5\left(8\right)\right)\right]:\frac{50}{53}\)
c)\(\frac{0,375-0,3+\frac{3}{11}+\frac{3}{12}}{0,625-0,5+\frac{5}{11}+\frac{5}{12}}\)
Tính :
A = \(\left(1-\frac{2}{3}+\frac{4}{3}\right)-\left(\frac{4}{5}-1\right)+\left(\frac{7}{5}+2\right)\)
B = \(\left(-3+\frac{3}{4}-\frac{1}{3}\right):\left(5+\frac{2}{5}-\frac{2}{3}\right)\)
C = \(\left(\frac{3}{5}-\frac{4}{5}\right).\left(\frac{2}{7}-\frac{3}{14}\right)-\left(\frac{5}{9}-\frac{7}{27}\right).\left(1-\frac{3}{5}\right)+\left(1-\frac{11}{12}\right).\left(1-\frac{11}{12}\right)\)
Tính :
a) \(5\dfrac{1}{3}+2,5.\left(\dfrac{1}{3}-\dfrac{5}{12}\right)\)
b) \(\sqrt{12^2-44}-\left(1\dfrac{3}{4}-2\right)^2+\left(-1.5\right)^5:\left(\dfrac{-3}{2}\right)^4\)
Tính
B=\(\dfrac{\left(\dfrac{2}{3}\right)^3.\left(\dfrac{-3}{4}\right)^2.\left(-1\right)^{2011}}{\left(\dfrac{2}{5}\right)^2.\left(\dfrac{-5}{12}\right)^3}\)
Tính:
a) \(\frac{\left[\left(-2\right)^2\right]^5}{\left(-2\right)^3\left(-2\right)^2\left(-4\right)^2}\)b) \(\frac{4^6.9^5+6^9.120}{8^4.3^{12}-6}\)1. Tính hợp lí :
a) \(\frac{3}{4}-0,25-\left[\frac{7}{3}+\left(\frac{-9}{2}\right)\right]-\frac{5}{6}\)
b) 7 + \(\left(\frac{7}{12}-\frac{1}{2}+3\right)-\left(\frac{1}{12}+5\right)\)
2. Tìm các sô nguyên x biết:
\(\frac{3}{4}-\frac{5}{6}\le\frac{x}{12}< 1-\left(\frac{2}{3}-\frac{1}{4}\right)\)
Thực hiện các phép tính :
a) \(9,6.2\dfrac{1}{2}-\left(2.125-1\dfrac{5}{12}\right):\dfrac{1}{4}\)
b) \(\dfrac{5}{18}-1,456:\dfrac{7}{25}+4,5.\dfrac{4}{5}\)
c) \(\left(\dfrac{1}{2}+0,8-1\dfrac{1}{3}\right)\left(2,3\right)+4\dfrac{7}{25}-1,28\)
d) \(\left(-5\right).12:\left[\left(-\dfrac{1}{4}\right)+\dfrac{1}{2}:\left(-2\right)\right]+1\dfrac{1}{3}\)
ĐỀ 2:
1. Tính:
A. \(\left(-\dfrac{2}{3}\right)^2+\left(-\dfrac{7}{8}\right)+\left(-\dfrac{11}{12}\right)\)
B. \(\left(\dfrac{-1}{3}\right)^2:\dfrac{1}{6}-2.\left(\dfrac{-1}{2}\right)^3\)\
C. \(\dfrac{-1}{5}-\left(\dfrac{1}{2}+\dfrac{3}{4}\right)^2:\dfrac{5}{8}\)
D. \(\left|\dfrac{-3}{2}+1,2\right|+1\dfrac{2}{3}:6\)
2. Tìm x, biết:
a. \(\dfrac{2}{3}x-\dfrac{1}{3}x=\dfrac{5}{12}\)
b. \(\left(x-\dfrac{12}{7}\right):1\dfrac{1}{5}=\dfrac{4}{7}\)
c. \(\dfrac{2}{5}+\left|x+1\right|=\dfrac{3}{4}\)
3. Tìm x, y biết:
a. \(\dfrac{x}{18}=\dfrac{y}{15}\)và x - y = -30
b. 7x = 9x và 10x - 8x = 68
c. \(\left(x-\dfrac{1}{2}\right)^{50}+\left(y+\dfrac{1}{3}\right)^{40}=0\)
* Lm nhanh nha