a,  15 . { 32 : [ 6 - 5 + 5 ( 9 : 3 ) ] + 3 } - 2018 0

= 15.{32:[1+15]+3}–1

= 15.5–1

= 74

b,  25 . { 2 7 : [ 12 - 4 + 2 2 . 16 : 2 3 ] - 2 4 }

= 25.{128:[8+4.2]–16}

= 25.24

= 600

c,  2019 . { 101 - 1000 : [ 2 2 . 2 3 + 5 6 : 5 3 - 6 2 : 11 - 2018 0 ] }

= 2019.{101–1000:[(32+125–36):11–1]}

= 2019.{101–1000:[121:11–1]}

= 2019.{101–1000:10}

= 2019.1

= 2019

\(1,\\ a,\Leftrightarrow4^{5-x}=4^2\Leftrightarrow5-x=2\Leftrightarrow x=3\\ b,\Leftrightarrow\left[{}\begin{matrix}x-1=5\\x-1=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=6\\x=-4\end{matrix}\right.\\ c,\Leftrightarrow2x+1=3\Leftrightarrow x=2\\ 2,\\ a,3^{100}=\left(3^2\right)^{50}=9^{50}\\ b,2^{98}=\left(2^2\right)^{49}=4^{49}< 9^{49}\\ c,5^{30}=5^{29}\cdot5< 6\cdot5^{29}\\ d,3^{30}=\left(3^3\right)^{10}=27^{10}>8^{10}\\ 4,\\ a,\Leftrightarrow5\left(x-10\right)=10\\ \Leftrightarrow x-10=2\Leftrightarrow x=12\\ b,\Leftrightarrow3\left(70-x\right)+5=92\\ \Leftrightarrow3\left(70-x\right)=87\\ \Leftrightarrow70-x=29\\ \Leftrightarrow x=41\\ c,\Leftrightarrow16+x-5=315-230=85\\ \Leftrightarrow x=74\\ d,\Leftrightarrow2^x-5+74=707:\left(16-9\right)=707:7=101\\ \Leftrightarrow2^x=32=2^5\\ \Leftrightarrow x=5\)

bài 4 đâu bạn r =))

18:

a: \(S=3\left(\dfrac{2}{2\cdot4}+\dfrac{2}{4\cdot6}+...+\dfrac{2}{98\cdot100}\right)\)

=3*(1/2-1/4+1/4-1/6+...+1/98-1/100)

=3*49/100=147/100

b: Để A là số nguyên thì n-1 thuộc Ư(2)

=>n-1 thuộc {1;-1;2;-2}

=>n thuộc {2;0;3;-1}

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  C=5.4+8.4-2

 D=5+8-4-2 từ đó suy ra C>D

chi oi ,em la hoc sinh lop 4 o truong tieu hoc thi tran bac son.huyen bac son,tinh lang son.em khong biet cau hoi cua chi tra loi the nao nhung em biet chi biet ve 12 cung hoang dao dunh khong.con em la cung thien binh.em rat mong duoc ket ban voi chi

Bài 1 :

\(M=\dfrac{30-2^{20}}{2^{18}}=\dfrac{2.15-2^{20}}{2^{18}}=\dfrac{15}{2^{17}}-2^2=\dfrac{15}{2^{17}}-4< 0\left(\dfrac{15}{2^{17}}< 1\right)\)

\(N=\dfrac{3^5}{1^{2021}+2^3}=\dfrac{3^5}{9}=\dfrac{3^5}{3^2}=3^3=27\)

\(\Rightarrow M< N\)

Bài 3 :

a) \(t^2+5t-8\) khi \(t=2\)

\(=5^2+2.5-8\)

\(=25+10-8\)

\(=27\)

b) \(\left(a+b\right)^2-\left(b-a\right)^3+2021\left(1\right)\)

\(\left\{{}\begin{matrix}a=5\\b=a+1=6\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}a+b=11\\b-a=1\end{matrix}\right.\)

\(\left(1\right)=11^2-1^3+2021=121-1+2021=2141\)

c) \(x^3-3x^2y+3xy^2-y^3=\left(x-y\right)^3\left(1\right)\)

\(\left\{{}\begin{matrix}x=3\\y=2\end{matrix}\right.\) \(\Rightarrow x-y=1\)

\(\left(1\right)=1^3=1\)

B lớn hơn

thu gọn 7^3*7^5

cặk cặk

[545 - (45 + 4 x 25)] : 50 - 200 : 250 + 2¹⁵ : 2¹³

= [545 - (45 + 100)] : 50 - 200 : 250 + 2²

= (545 - 4500) : 50 - 200 : 254

= (-3955) : 50 + 200 : 254

= [(-3955) + 200] : (50 + 254)

= (-3755) : 304

= bạn tự tính nha

[504 - (25 x 8 + 70)] : 9 - 15 + 19⁰

= [504 - (200 + 70)] : 9 - 15 + 0

= (504 - 270) : 9 - 15

= 234 : 9 - 15

= 26 - 15

= 9

5 x {26 - [3 x 5 + 2 x 5 + 15] : 15}

= 5 x {26 - [(3 + 2) x 5) + 15] : 15}

= 5 x {26 - [5 x 5 + 15] : 15}

= 5 x [26 - (25 + 15) : 15]

= 5 x (26 + 25 - 15 : 15)

= 5 x (51 - 1)

= 5 x 50 = 250

d) [1104 - (25 x 8 + 40)] : 9 + 3¹⁶ : 3¹²

= [1104 - (200 + 40)] : 9 + 3⁴

= (1104 - 240) : 9 + 81

= 864 : 9 + 81

= 96 + 81

= 177

Học tốt!!!