Câu 1:
57x26+57x43+57x31
= 57x(26+43+31)
= 57x100
=5700
Câu 2:
177x 56- 56x56+ 121x44
= (177-56)x 56+ 121x44
= 122x56 + 121x44
= 121x(56+44)
=121x100
=12100
\(57.26+57.43+57.31\)
\(=57.\left(26+43+31\right)\)
\(=57.100\)
\(=5700\)
\(177.56-56.56+121.44\)
\(=56.\left(177-56\right)+121.44\)
\(=56.121+121.44\)
\(=121.\left(56+44\right)\)
\(=121.100\)
\(=12100\)
\(68.42+34.16\)
\(=34.2.42+34.16\)
\(=34.84+34.16\)
\(=34\left(84+16\right)\)
\(=34.100\)
\(=3400\)