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= ( 515.5.3 + 29.516): 516.24
= 516(3+29) : 516.24
= 516.25 : 516.24 = 2
( vì 3+29 = 32 =25)
S=5^16+4.5^15+7^16+11.7^15
=5^15.5+4.5^15+7^15.7+11.7^15
=5^15(5+4)+7^15(7+11)
=5^15.9+7^15.18
=5^15.9+7^15.2.9
S=9(5^15+7^15.2) chia hết cho 9(đpcm)
(315. 4 + 5. 315):316
=[315. (4+5)]:316
=[315. 9]: 316
=[315. 32]:316
=\(\frac{3^{15}.3^2}{3^{16}}=\frac{3^2}{3}=\frac{9}{3}=3\)
(315 . 4 + 5 . 315) : 316
= 315 . (4 + 5) : 316
= 315 . 9 : 316
= 315 . 32 : 316
= 317 : 316
= 3
áp dụng tc \(\frac{a}{b}< 1\Rightarrow\frac{a+m}{a+m}< 1\left(m\in N\right)\)
Ta có: \(B=\frac{15^{16}+1}{15^{17}+1}< \frac{15^{16}+1+14}{15^{17}+1+14}\)\(=\frac{15^{16}+15}{15^{17}+15}=\frac{15.\left(15^{15}+1\right)}{15.\left(15^{16}+1\right)}=\frac{15^{15}+1}{15^{16}+1}\)
\(\Rightarrow B< A\)
\(A=\frac{15^{15}+1}{15^{16}+1}\)
\(\Rightarrow15A=\frac{15^{16}+15}{15^{16}+1}\)
\(\Rightarrow15A=\frac{15^{16}+1+14}{15^{16}+1}\)
\(\Rightarrow15A=\frac{15^{16}+1}{15^{16}+1}+\frac{14}{15^{16}+1}\)
\(\Rightarrow15A=1+\frac{14}{15^{16}+1}\)
\(B=\frac{15^{16}+1}{15^{17}+1}\)
\(\Rightarrow15B=\frac{15^{17}+15}{15^{17}+1}\)
\(\Rightarrow15B=\frac{15^{17}+1+14}{15^{17}+1}\)
\(\Rightarrow15B=\frac{15^{17}+1}{15^{17}+1}+\frac{14}{15^{17}+1}\)
\(\Rightarrow15B=1+\frac{14}{15^{17}+1}\)
Vì \(\frac{14}{15^{17}+1}< \frac{14}{15^{16}+1}\) nên \(15B< 15A\)
Vậy B < A
Ta có công thức \(\frac{a}{b}<1\)thì\(\frac{a}{b}<\frac{a+n}{b+n}\)
\(B=\frac{15^{16}+1}{15^{17}+1}<\frac{15^{16}+1+14}{15^{17}+1+14}=\frac{15^{16}+15}{15^{17}+15}=\frac{15\left(15^{15}+1\right)}{15\left(15^{16}+1\right)}=\frac{15^{15}+1}{15^{16}+1}=A\left(1\right)\)
từ (1) \(\Leftrightarrow A>B\)
Chú thích : mình không ghi được phân số trên pad nên /có nghĩa là vd 4/7 là bốn phần bảy nha.
a, \(\frac{25^{11}.4^{33}}{8^{15}.10^{22}}=\frac{\left(5^2\right)^{11}.\left(2^2\right)^{33}}{\left(2^3\right)^{15}.\left(2.5\right)^{22}}=\frac{5^{22}.2^{66}}{2^{45}.2^{22}.5^{22}}=\frac{5^{22}.2^{66}}{2^{67}.5^{22}}=\frac{1}{2}\)
b,\(\frac{8^4.5^8.9^3}{125^3.4^7.27}=\frac{\left(2^3\right)^4.5^8.\left(3^2\right)^3}{\left(5^3\right)^3.\left(2^2\right)^7.3^3}=\frac{2^{12}.5^8.3^6}{5^9.2^{14}.3^3}=\frac{3^3}{5.2^2}=\frac{27}{20}\)
Bạn làm nốt nhé cũng tương tự thôi !!!!!!!!!
(515\(\times\) 4 + 1515): 516
= (515.4 + 315.515): 516
= 515.( 4 + 315):516
= (515: 516).(4 + 315)
= \(\dfrac{1}{5}\).(4 + 315)
515×× 4 + 1515): 516
= (515.4 + 315.515): 516
= 515.( 4 + 315):516
= (515: 516).(4 + 315)
= 1551.(4 + 315