a: \(4^{10}\cdot2^{30}=2^{30}\cdot2^{20}=2^{50}\)

b: \(9^{25}\cdot27^4\cdot81^2=3^{50}\cdot3^{12}\cdot3^8=3^{70}\)

c: \(25^{50}\cdot125^5=5^{100}\cdot5^{15}=5^{115}\)

d: \(64^3\cdot4^8\cdot16^4=4^9\cdot4^8\cdot4^8=4^{25}\)

e: \(2^{10}:8^3=2^{10}:2^9=2\)

\(12^7:6^7=\left(\dfrac{12}{6}\right)^7=2^7\)

f: \(5^8:25^2=5^8:5^4=5^4\)

\(4^9:64^2=4^9:4^6=4^3\)

\(2^{25}:32^4=2^{25}:2^{20}=2^5\)

\(125^3:25^4=5^9:5^8=5\)

g: 2^5*8^4

=2^5*(2^3)^4

=2^5*2^12

=2^17

a: \(A=\dfrac{\left(258-242\right)\left(258+242\right)}{\left(254-246\right)\left(254+246\right)}=\dfrac{16}{8}=2\)

b: \(=\left(263+37\right)^2=300^2=90000\)

c: \(=\left(136-46\right)^2=90^2=8100\)

d: \(=50^2-49^2+48^2-47^2+...+2^2-1^2\)

=50+49+...+2+1

=51x50:2=1275

a) Số số hạng của tổng là:

         (407-1):2+1=204(số hạng )

Từ đó ,ta có:\(\Rightarrow\)S=1+3-5-7+9+11-...-405-407

                    \(\Rightarrow\)(1+3-5-5)+(9+11-13-15)+...+(401+403-405-407)                                                                                                                                  \(\Rightarrow\)(-8)+(-8)+...+(-8) (51 số -8)

                    \(\Rightarrow\)-8.51=-408

a) Số số hạng của tổng là:

         ( 407 - 1 ) : 2 + 1 = 204 ( số hạng )

Từ đó ,ta có:\(⇒\)S = 1 + 3 - 5 - 7 + 9 + 11 - ... - 405 - 407

                    ⇒( 1 + 3 - 5 - 5 ) + ( 9 + 11 - 13 - 15 ) + ... + ( 401 + 403 - 405 - 407 )                                                                                                                                  ⇒( - 8 ) + ( - 8 ) + ... + ( - 8 ) . ( 51 số - 8 )

                    ⇒- 8 . 51 = - 408

236. A) worked B) stopped C) forced
D) wanted
237. A) breathe B) breath C) sea
D) seat
238. A) think B) thanks C) three
D) that
239. A) emit B) erosion C) decree
D) problem
240. A) preserve B) conserve C) present
D) visitor
241. A) developed B) drained C) washed
D) conserved
242. A) women B) wonder C) one
D) come
243. A) entrusted B) liked C) distributed
D) included
244. A) honest B) house C) hour
D) heir
245. A) art B) paper C) lazy
D) late
246. A) mountain B) blouse C) ground
D) soup
247. A) manure B) pasture C) Adventure
D) measure
248. A) supposed B) collected C) Admired
D) posed
249. A) quiet B) activity C) title
D) quite
250. A) butter B) put C) sugar
D) push
251. A) few B) new C) threw
D) knew
252. A) pretty B) get C) send
D) well
253. A) master B) transitional C) spot
D) sound
254. A) dispose B) poisonous C) pollution
D) Atmosphere
255. A) pleasure B) lead C) release
D) unpleasant
256. A) nitrogen B) fertile C) dirty
D) oxide
257. A) transitive B) determine C) keenness
D) satisfaction
258. A) occupy B) ready C) puppy
D) study
259. A) five B) give C) hire
D) dive
260. A) comb B) bomb C) lamb
D) tomb

Ngữ âm?Là trọng âm ý ạ?

Ta có: B=1+2-3-4+...+251+252-253-254

=(1-2-3+4)+(5-6-7+8)+...+(251-252-253+254)

= 0+0+...+0

=0

\(B=1+2-3-4+...+251+252-253-254\) 

\(B=\left(1+2-3-4\right)+...+\left(251+252-253-254\right)\) 

\(B=-4+...+\left(-4\right)\) 

\(B=-4.63,5\) 

\(B=-254\)

A

A

-246

A

A

A

2^2.3^3.7

D. 252 = 2².3².7.

D nhưng mik ko có số bé để ửite bn nhek