a. 35.34 + 35.86 + 65.75 + 65.45

= 35.(34 + 86) + 65.(75 + 45)

= 35.120 + 65.120

= 120.(35 + 65)

= 120.100

= 12000

b. 21.7² - 11.7² + 90.7² + 49.1258.16

= 21.7² - 11.7² + 90.7² + 7².1258.16

= 7².(21 - 11 + 90 + 1258.16)

= 7².20228

= ... (Không tính nhanh được :3).

a. 35.34 + 35.86 + 65.75 + 65.45

= 35.(34 + 86) + 65.(75 + 45)

= 35.120 + 65.120

= 120.(35 + 65)

= 120.100

= 12000

b. 21.7² - 11.7² + 90.7² + 49.1258.16

= 21.7² - 11.7² + 90.7² + 7².1258.16

= 7².(21 - 11 + 90 + 1258.16)

= 7².20228

= ... (Không tính nhanh được :3).

A = \(\dfrac{21^2.14.125}{35^5.6}\)

= \(\dfrac{\left(3.7\right)^2.\left(2.7\right).5^3}{\left(5.7\right)^5.\left(2.3\right)}\)

= \(\dfrac{3^2.7^2.2.7.5^3}{5^5.7^5.2.3}\)

= \(\dfrac{3^2.7^3.2.5^3}{5^5.7^5.2.3}\)

= \(\dfrac{3}{5^2.7^2}\)

= \(\dfrac{3}{35^2}\)

@Pham Thi Thu Trang

B = \(\dfrac{2^{10}.13+2^{10}.65}{2^8.104}\)

= \(\dfrac{2^{10}\left(13+65\right)}{2^8.104}\)

= \(\dfrac{2.78}{104}\)

= \(\dfrac{3}{2}\)

@Pham Thi Thu Trang

a, \(35\times34+35\times86+65\times75+65\times45\)

\(=35\times(34+86)+65\times(75+45)\)

\(=35\times120+65\times120\)

\(=(35+65)\times120=100\times120=12000\)

b, \(21\times7^2-11\times7^2+90\times7^2+49\times125\times16\)

Làm nốt

a)35 x 34 + 35x 86 + 65 x 75 + 65 x 45

=35 x (34+86) + 65 x (75 + 45)

=35 x 120 + 65 x 120

=120 x (35 + 65)

=120 x 100

=12000

Chúc học tốt!

\(\left[116-\left(13-5^2\right)\right]=\left[116-\left(13-25\right)\right]=116-13+25=128\)

\(\frac{7^{25}}{7^{21}\times46+7^{21}\times3}=\frac{7^{25}}{7^{21}\times\left(46+3\right)}=\frac{7^4}{50}\)

\(57+212+43+288=\left(57+43\right)+\left(212+288\right)=100+500=600\)

\(28\times69+4\times18\times7+2\times14\times13=28\times69+18\times28+28\times13=28\times\left(69+18+13\right)=28\times100=2800\)

a) 5+96=101

( 7²⁰⁰+7¹⁹⁹) : 7¹⁹⁸  = 7²⁰⁰ : 7¹⁹⁸ + 7¹⁹⁹ : 7¹⁹⁸ = 49  + 7 = 56

 ( 7³+7²)x(5³+ 5⁶)x ( 3³x 3-9²) =  ( 7³+7²).(5³+ 5⁶) . ( 3^4 - 3^4) = ( 7³+7²).(5³+ 5⁶) . 0 = 0

câu c thì bn xem lại đề nha 2³x7x5³-( 5²x 65+ 5^{2x 35}) hay 2³x7x5³-( 5²x 65+ 5² x 35)

Dấu "." là dấu nhân

Bg

 (7⁶⁵.23 + 7⁶⁵.26) : 7⁶⁴ - 2⁶.5

= 7⁶⁵.(23 + 26) : 7⁶⁴ - 2⁶.5

= 7⁶⁵.49 : 7⁶⁴ - 2⁶.5

= 7⁶⁵.7² : 7⁶⁴ - 2⁶.5

= 7⁶⁷ : 7⁶⁴ - 2⁶.5

= 7³ - 2⁶.5

= 343 - 64.5

= 343 - 320

= 23

Ta có: \(\left(7^{65}\times23+7^{65}\times26\right):7^{64}-2^6\times5\)

     \(=7^{65}\times\left(23+26\right):7^{64}-64\times5\)

     \(=7\times49-64\times5\)

     \(=7\times49-64\times5\)

     \(=343-320\)

     \(=23\)

7⁴⁵-7⁴⁴ = 7⁴⁴-7⁴³

Vì:7⁴⁵-7⁴⁴=7

    7⁴⁴-7⁴³=7

quá dễ:7⁴⁵-7⁴⁴>7⁴⁴-7⁴³ vì có 7⁴⁵>7⁴³,7⁴⁴=7⁴⁴