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\(\text{a.61 x 23 + 39 x 22}\)

\(=61.22+1+39.22\)

\(=22.\left(61+39\right)+1\)

\(=22.100+1\)

\(=2200+1\)

\(=2201\)

mình chỉ làm được 1 câu thôi

hok tốt

61*23+39*22

=(61+39)*22+61

=100*22+61

=2200+61

=2261

111/112x112/113x113/114x114/115x116/117=111/117 nha

vì 112 rút gọn 112 ,113 cũng như thế đến 116 song chỉ còn 111 và 117

nha bạn

A = \(\dfrac{2}{35}\) + \(\dfrac{4}{77}\) + \(\dfrac{2}{143}\) + \(\dfrac{4}{221}\) + \(\dfrac{2}{323}\) + \(\dfrac{4}{437}\) + \(\dfrac{2}{575}\)

A =  \(\dfrac{2}{5\times7}\)+\(\dfrac{4}{7\times11}\)+\(\dfrac{2}{11\times13}\)+\(\dfrac{4}{13\times17}\)+\(\dfrac{2}{17\times19}\)+\(\dfrac{4}{19\times23}\)+\(\dfrac{2}{23\times25}\)

A = \(\dfrac{1}{5}\)-\(\dfrac{1}{7}\)+ \(\dfrac{1}{7}\) - \(\dfrac{1}{11}\)+\(\dfrac{1}{11}\)-\(\dfrac{1}{13}\)+\(\dfrac{1}{13}\)-\(\dfrac{1}{17}\)+\(\dfrac{1}{17}\)-\(\dfrac{1}{19}\)+\(\dfrac{1}{19}\)-\(\dfrac{1}{23}\)+\(\dfrac{1}{23}\)-\(\dfrac{1}{25}\)

A = \(\dfrac{1}{5}\) - \(\dfrac{1}{25}\)

A = \(\dfrac{4}{25}\)

45 x ( 55 + 117 ) + 55 x ( 117 - 45 )

= (45 x 55 - 45 x 55) + (45 + 55) x 117

= 0  + 100 x 117 = 11700

\(45\times\left(55+117\right)+55\times\left(117-45\right)\)

\(=45\times55+45\times117+55\times117-55\times45\)

\(=\left(45\times55-45\times55\right)+45\times117+55\times117\)

\(=45\times117+55\times117\)

\(=117\times\left(45+55\right)\)

\(=117\times100\)

\(=11700\)