Tính nhanh: H=7/13 × 5/19 +7/19 ×8/13 -3 × 7/19
2 câu trả lời
`7/13 xx 5/19 +7/19 xx 8/13 -3 xx 7/19`
`H= (7xx5)/(13xx19)+ 7/19 xx 8/13 - 3 xx 7/19`
`H= 7/19 × 5/13 +7/19 ×8/13 -3 × 7/19`
`H= 7/19 xx (5/13 + 8/13 - 3)`
`H= 7/19 xx (13/13 -3)`
`H= 7/19 xx (1-3)`
`H= 7/19 xx (-2)`
`H= (7.(-2))/19`
`H= -14/19`
Vậy `H=-14/19`
`H=7/13 × 5/19 +7/19 ×8/13 -3 × 7/19`
`= (7xx5)/(13xx19)+ 7/19 xx 8/13 - 3 xx 7/19`
`= (7xx5)/(19xx13)+ 7/19 xx 8/13 - 3 xx 7/19`
`= 7/19 × 5/13 +7/19 ×8/13 -3 × 7/19`
`= 7/19 xx (5/13 + 8/13 - 3)`
`= 7/19 xx (13/13 -3)`
`= 7/19 xx (1-3)`
`= 7/19 xx (-2)`
`= (7.(-2))/19`
`= -14/19`
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