\(\text{C. (-3) –(4- 6) = -1}\)

;C

C

3.5^2-27:3^2+5^2.4-18:3^2

=3.25-27:9+25.4+18:9

= 75-3+100+2

= 174

9*8*48+7*4*48+72*52+2*52*14

=72*48+28*48+72*52+28*52

=72 * ( 48 + 52 ) + 28 * ( 48 + 52 )

=72 * 100 + 28 * 100

=100 * ( 72 + 28 )

= 100 * 100

=10000

9 x 8 x 48 + 7 x 4 x 48 + 72 x 52 + 2 x 52 x 14 

= 72 x 48 + 28 x 48 + 72 x 52 + 2 x 14 x 52

= ( 72 + 28 ) x 48 + 72 x 52 + 28 x 52

= ( 72 + 28 ) x 48 + ( 72 + 28 ) x 52

=  100 x 48 + 100 x 52

= 100 x ( 48 + 52 )

= 100 x 100

= 10000

9 . 8 . 48 + 7 . 4 . 48 + 72 . 52 + 2 . 52 . 14

= 72 . 48 + 28 . 48 + 72 . 52 + 52 . 28

= 48 . ( 72 + 28 ) + 52 . ( 72 + 28 )

= 48 . 100 + 52 .100

= 100 . ( 48 + 52 )

= 100 . 100

= 10000

\(a,\\ 52^2+52.48=52.52+52.48=52.\left(52+48\right)=52.100=5200\\ b,\\ 39^2-39.29=39.39-39.29=39.\left(39-29\right)=39.10=390\\ c,\\ 99.5^3+125=99.125+125=125.\left(99+1\right)=125.100=12500\)

a) 52² + 52 . 48 = 2704 + 2496 = 5200

b) 39² - 39 . 29 = 1521 - 1131 = 390

c) 99 . 5³ + 125 = 99 . 125 + 125 = 12375 + 125 = 12400

\(B=\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+\frac{1}{3\cdot4\cdot5}+\frac{1}{18\cdot19\cdot20}\)

\(B=\frac{1}{2}\left(\frac{2}{1\cdot2\cdot3}+\frac{2}{2\cdot3\cdot4}+\frac{2}{3\cdot4\cdot5}+\frac{2}{18\cdot19\cdot20}\right)\)

\(B=\frac{1}{2}\left(\frac{1}{1\cdot2}-\frac{1}{2\cdot3}+\frac{1}{2\cdot3}-\frac{1}{3\cdot4}+\frac{1}{3\cdot4}-\frac{1}{4\cdot5}+...+\frac{1}{18\cdot19}-\frac{1}{19\cdot20}\right)\)

\(B=\frac{1}{2}\left(\frac{1}{1\cdot2}-\frac{1}{19\cdot20}\right)\)

\(B=\frac{1}{2}\cdot\frac{189}{380}=\frac{189}{760}\)

\(C=\frac{52}{1\cdot6}+\frac{52}{6\cdot11}+\frac{52}{11\cdot16}+...+\frac{52}{31\cdot36}\)

\(C=\frac{52}{5}\left(\frac{5}{1\cdot6}+\frac{5}{6\cdot11}+\frac{5}{11\cdot16}+...+\frac{6}{31\cdot36}\right)\)

\(C=\frac{52}{5}\left(1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+\frac{1}{11}-\frac{1}{16}+...+\frac{1}{31}-\frac{1}{36}\right)\)

\(C=\frac{52}{5}\cdot\left(1-\frac{1}{36}\right)\)

\(C=\frac{91}{9}\)

Bạn ơi số âm phải có dấu ngoặc nhé để không bị lộn với dấu trừ

(-15)+17-22+15-17+22=0

5-14+52-4+14-52+4=5

K mình nhé! ^_^

a) -15 + 17 - 22 + 15 - 17 + 22

 = (-15 + 15) + (17 - 17) + (-22 + 22)

= 0 + 0 + 0

=0

b) 5 - 14 + 52 - 4 + 14 - 52 + 4

= 5 + (-14 + 14) + (52 - 52) + (-4 + 4)

= 5 + 0 + 0 + 0

= 5

Chúc bạn học tốt !

cảm ơn cún kì lân đã góp ý nha

Tính nhanh : 

52 . (-67) - 52 . (-43) + 24 . (-48)

= 52 . [ (-67) - ( -43)  ] + 24 . (-48)

= 52 . (-24) + 24 . (-48)

= (-52) . 24 + 24 . (-48)

= 24 . [ (-52) + (-48) ]

= 24 . (-100)

= - 2400

(-12) . 7 + (-8) . 7 + 4 . (-25) + (-6) . (-25)

= 7 . [ (-12) + (-8) ] + (-100 ) + (-6) . (-25)

= 7 . (-20) - 100 + (-6) . (-25)

= (-140) - 100 + 150

= (-240) + 150

= -90 

a: Sai

b: S

c: Đ

d: S

a,S

b,S

c,Đ

d,S

a) S

b) S

c) Đ

d) S

a: x-56:4=16

nên x-14=16

hay x=30

b: \(101+\left(36-4x\right)=105\)

\(\Leftrightarrow36-4x=4\)

hay x=8

Vì a: x-56:4=16

    =>x-14=16

   Hay:x=30

Vì b: 

   Hay:x=8

         Vậy x={30:8}

 Nếu sai thì thui nhá,đừng chửi mình!