So sánh
\(a,\left(-5\right)^{30}\&\left(-3\right)^{50}\)
\(b,\left(\frac{1}{16}\right)^{10}\&\left(\frac{1}{2}\right)^{50}\)
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Ta có : (-5)30 = (-53)10 = (-125)10 = 12510
(-3)50 = (-35)10 = (-243)10 = 24310
Mà : 12510 < 24310
Nên : (-5)30 < (-3)50
(-5)30=(-5)3.10=((-5)3)10=(-125)10
(-3)50=((-3)5.10=((-3)5)10=(-243)10
vì 125<243 nên (-125)10<(-243)10
\(\left(\frac{1}{10}\right)^{30}=\frac{1}{10^{30}}=\frac{10^{10}}{10^{40}}\)
\(\left(\frac{3}{10}\right)^{40}=\frac{3^{40}}{10^{40}}\)
\(3^{40}=\left(3^4\right)^{10}=81^{10}\)
\(\Rightarrow3^{40}\)>\(10^{10}\)
\(\Rightarrow\left(\frac{3}{10}\right)^{40}\)>\(\left(\frac{1}{10}\right)^{30}\)
\(B=24\left(5^2+1\right)\left(5^4+1\right)\left(5^8+1\right)\left(5^{16}+1\right)\)
\(=\left(5^2-1\right)\left(5^2+1\right)\left(5^4+1\right)\left(5^8+1\right)\left(5^{16}+1\right)\)
\(=\left(5^4-1\right)\left(5^4+1\right)\left(5^8+1\right)\left(5^{16}+1\right)\)
\(=\left(5^8-1\right)\left(5^8+1\right)\left(5^{16}+1\right)\)
\(=\left(5^{16}-1\right)\left(5^{16}+1\right)\)
\(=5^{32}-1< 5^{32}\)
Vậy \(B< A\)
\(A=x+\left(x+\frac{1}{5}\right)+\left(x+\frac{2}{5}\right)+\left(x+\frac{3}{5}\right)+\left(x+\frac{4}{5}\right)\)
\(=5x+\frac{1}{5}+\frac{2}{5}+\frac{3}{5}+\frac{4}{5}\)
\(=5x+2\)
\(B=5x\)
\(\Rightarrow A>B\)Với \(\forall\)\(x\)
#)Giải :
\(A=\left[x\right]+\left[1+\frac{1}{5}\right]+\left[x+\frac{2}{5}\right]+\left[x+\frac{3}{5}\right]+\left[x+\frac{4}{5}\right]\)
Thay x = 3,7 vào biểu thức, ta có :
\(A=\left[3,7\right]+\left[3,7+\frac{1}{5}\right]+\left[3,7+\frac{2}{5}\right]+\left[3,7+\frac{3}{5}\right]+\left[3,7+\frac{4}{5}\right]\)
\(A=\left[3,7+3,7+3,7+3,7+3,7\right]+\left[1+\frac{1}{5}+\frac{2}{5}+\frac{3}{5}+\frac{4}{5}\right]\)
\(A=18,5+3\)
\(A=21,5\)
\(B=\left[5x\right]=\left[5\times3,7\right]=18,5\)
Vì 21,5 > 18,5 \(\Rightarrow A>B\)
(-0,8)30=(0,8)30
(0,4)60=(0,4)30.2=((0,4)2)30=(0,16)30
Vì: (0,16)30<(0,8)30 (0,16<0,8)
=> (0,4)60 < (-0,8)30
\(5A=5+5^2+5^3+..+5^{151}\)
\(5A-A=\left(5+5^2+...+5^{151}\right)-\left(1+5+..+5^{150}\right)\)
\(4A=5^{151}-1\)
\(A=\dfrac{5^{151}-1}{4}\)
Nếu mình không nhầm thì dấu chia bạn đánh nhầm thành dấu chia hết
=> A < B
a)
Vì 3<5
\(\Rightarrow3^{30}< 5^{30}\)
\(\Rightarrow\left(-3\right)^{30}< \left(-5\right)^{30}\)
b)
Ta có
\(\left(\frac{1}{2}\right)^{50}=\left[\left(\frac{1}{2}\right)^4\right]^{10}.\left(\frac{1}{2}\right)^{10}\)
\(=\left(\frac{1}{16}\right)^{10}.\left(\frac{1}{2}\right)^{10}\)
Ta có
\(\left(\frac{1}{2}\right)^{10}< 1\)
\(\Leftrightarrow\left(\frac{1}{16}\right)^{10}.\left(\frac{1}{2}\right)^{10}< \left(\frac{1}{16}\right)^{10}\)
\(\Leftrightarrow\left(\frac{1}{2}\right)^{50}< \left(\frac{1}{16}\right)^{10}\)
câu a bạn nhầm đề ạ ^^