\(2C=2+6+12+20+...+2450\)

\(2C=1.2+2.3+3.4+4.5+...+49.50\)

\(6C=1.2.3+2.3.3+3.4.3+...+49.50.3\)\(6C=1.2.3+2.3.\left(4-1\right)+3.4.\left(5-2\right)+...+49.50.\left(51-48\right)\)

\(6C=1.2.3+2.3.4-1.2.3+...+49.50.51-49.50.51\)

\(6C=49.50.51\)

\(6C=124950\)

\(C=20825\)

a)237x24=5688

b)16050:75=214 nhé

???

\(c,\dfrac{12}{25}.\dfrac{-5}{24}=\dfrac{-60}{600}=-\dfrac{1}{10}\\ d,\dfrac{8}{15}:\dfrac{-4}{9}=\dfrac{8}{15}.\dfrac{9}{-4}=\dfrac{72}{-60}=-\dfrac{6}{5}\)

c) \(\dfrac{12}{25}.\dfrac{-5}{24}=\dfrac{12.\left(-5\right)}{25.24}=-\dfrac{1}{10}\)

d) \(\dfrac{8}{15}:\dfrac{-4}{9}=\dfrac{8}{15}\times\dfrac{-9}{4}=-\dfrac{6}{5}\)

a) \(\dfrac{12}{25}.\dfrac{-5}{24}=\dfrac{1.-1}{5.2}=\dfrac{-1}{10}\)

b) \(\dfrac{8}{15}:\dfrac{-4}{9}=\dfrac{8}{15}x\dfrac{-9}{4}=\dfrac{2.-3}{5.1}=\dfrac{-6}{5}\)

\(=\dfrac{27}{5}\cdot\dfrac{30}{7}+\dfrac{40}{7}\cdot\dfrac{37}{7}=\dfrac{2614}{49}\)

\(c)\)

\(5\dfrac{2}{5}\times4\dfrac{2}{7}+5\dfrac{5}{7}\times5\dfrac{2}{7}\)

\(=\dfrac{27}{5}\times\dfrac{30}{7}+\dfrac{40}{7}\times\dfrac{37}{7}\)

\(=\dfrac{162}{7}+\dfrac{40}{7}\times\dfrac{37}{7}\)

\(=\dfrac{162}{7}+\dfrac{1480}{49}\)

\(=\dfrac{1134}{49}+\dfrac{1480}{49}\)

\(=\dfrac{2614}{49}\)

C=1353400

Tick mk vài cái cho tròn 320 nha !!!

C=1353400

Sắp off rồi nên để lúc khác giải cho

\(c,\dfrac{5}{18}\times\dfrac{2}{15}:\dfrac{1}{5}\\ =\dfrac{1}{9}\times\dfrac{1}{3}\times5\\ =\dfrac{5}{27}\\ d,\dfrac{4}{13}+\dfrac{2}{11}:\dfrac{4}{33}\\ =\dfrac{4}{13}+\dfrac{2}{11}\times\dfrac{33}{4}\\ =\dfrac{4}{13}+\dfrac{3}{2}=\dfrac{8}{26}+\dfrac{39}{26}\\ =\dfrac{47}{26}\)

Đặt A=1.2.3+2.3.4+3.4.5+4.5.6+...+98.99.100

4A=(1.2.3+2.3.4+3.4.5+4.5.6+...+98.99.100)4

4A=1.2.3(4-0)+2.3.4(5-1)+3.4.5(6-2)+4.5.6(7-3)+...+98.99.100(101-97)

4A=1.2.3.4+2.3.4.5-1.2.3.4+3.4.5.6-2.3.4.5+4.5.6.7-3.4.5.6+...+98.99.100.101-97.98.99.100

4A=1.2.3.4-1.2.3.4+2.3.4.5-2.3.4.5+3.4.5.6-3.4.5.6+...+97.98.99.100-97.98.99.100+98.99.100.101

4A=98.99.100.101

=>A=98.99.100.101/4

=> A=24497550

c, 126 - (126 - 33)=126-126+33=33

d, (-53 - 23) - (567 - 53) =-76-567+53=-590

e, 145 - (23 - 45) - (-23 - 10) =145+22+33=200

 126 - ( 126 -33) = 126 -126 + 33 = 33

(-53-23)-(567-53)= -76 -567 + 53 = -590

145 - ( 23 -45) -( -23 -10) = 145 -23 + 45 +23 + 10= 200

c)= 126 - 126 + 33= 33

d) = -53 - 23 - 567 + 53 = (-53 + 53) - (23 + 567) =0 - 590 = -590

e)= 145 - 23 + 45 + 23 + 10= 145 + (-23 + 23 ) + (45 + 10)= 145 + 0+55= 145 + 55 =200