9700 : 100 + 36 x 12 = 529

(160 x 5 - 25 x 4) : 4= 175

108 x (23 + 7) = 3240

215 x 86 + 215 x 14 = 21500

3 x 128 - 43 x 128= -5120

529

175

3240

21500

-5120 (lớp 4 học âm hẻ)

529

175

3240

21500

....

a) 36 x 25 x 4 = 36 x ( 25 x 4) = 36 x 100 = 3600

18 x 24 : 9= 24 x ( 18:9) = 24 x 2 = 48

41 x 2 x 8 x 5= 41 x 8 x ( 5x2) = 41 x 8 x 10 = 3280

b) 108 x (23 + 7)= 108 x 30 = 3240 

215 x 86 + 215 x 14 = 215 x ( 86 + 14) = 215 x 100 = 21500 

53 x 128 – 43 x 128= 128 x ( 53 - 43) = 128 x 10 = 1280

\(a,35\times25\times4=36\times100=3600\)

\(18\times24:9=18:9\times24=2\times24=48\)

\(41\times2\times8\times5=\left(2\times5\right)\times\left(41\times8\right)=10\times328=3280\)

\(b,108\times\left(23+7\right)=108\times30=3240\)

\(215\times86+215\times14=215\times\left(86+14\right)=215\times100=21500\)

\(53\times128-43\times128=128\times\left(53-43\right)=128\times10=1280\)

các bạn ơi nhớ mình là ai không các bạn hay trả lời câu hỏi của mình đó

a ) x = 1 9 + 5 7 = 52 63 b ) x = 2 15 − 3 10 = − 1 6

c ) x = 2 45 − 1 9 = − 1 15 ; d ) x = − 3 7 − 4 5 − − 2 3 = − 59 105

a ) 3 10 . b ) 49 5 . c ) − 3. d ) − 15 6

Ta có: \(\left(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{8\cdot9}\right)\cdot x=\dfrac{23}{45}\)

\(\Leftrightarrow x\left(1-\dfrac{1}{9}\right)=\dfrac{23}{45}\)

\(\Leftrightarrow x=\dfrac{23}{45}\cdot\dfrac{9}{8}=\dfrac{23}{40}\)

giup mik vs

Đặt A bằng biểu thức trong ngoặc

\(2A=\dfrac{3-1}{1.2.3}+\dfrac{4-2}{2.3.4}+\dfrac{5-3}{3.4.5}+...+\dfrac{10-8}{8.9.10}\)

\(2A=\dfrac{1}{2}-\dfrac{1}{2.3}+\dfrac{1}{2.3}-\dfrac{1}{3.4}+\dfrac{1}{3.4}-\dfrac{1}{4.5}+...+\dfrac{1}{8.9}-\dfrac{1}{9.10}=\dfrac{1}{2}-\dfrac{1}{9.10}\)

\(2A=\dfrac{44}{90}\)

\(A=\dfrac{22}{90}\)

Ta có: \(\left(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+...+\dfrac{1}{8\cdot9}\right)\cdot x=\dfrac{23}{45}\)

\(\Leftrightarrow x\cdot\left(1-\dfrac{1}{9}\right)=\dfrac{23}{45}\)

\(\Leftrightarrow x=\dfrac{23}{45}:\dfrac{8}{9}=\dfrac{23}{45}\cdot\dfrac{9}{8}=\dfrac{23}{40}\)