CMR:
a) 742³-692³ chia hết cho200
b) 685³+315³ chia hết cho 25 000
CMR: a) 742³-692³ chia hết cho200 b) 685³+315³ chia hết cho 25 000
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CMR:
a) 742³-692³ chia hết cho200
b) 685³+315³ chia hết cho 25 000
Adela
Giải thích các bước giải:
a) `742^3-692^3`
`=(742-692)(742^2+742.692+692^2)`
`=(742-692)(371^2 .2^2+2.371.2.346+346^2 .2^)`
`=50.4(371^2+371.346+346^2)`
`=200(371^2+371.346+346^2)vdots200`
b) `685^3+315^3`
`=(685+315)(685^2-685.315+315^2)`
`=(685+315)(137^2 .5^2-5.137.5.63+63^2 .5^2)`
`=1000.25(137^2-137.63+63^2)`
`=25000(137^2-137.63+63^2)vdots25`