解:①(﹣20)+(+3)﹣(﹣5)﹣(+7)+7.2﹣(﹣4.8) =[(﹣20)﹣(﹣5)]+[(+3)﹣(+7)]+[7.2﹣(﹣4.8)] =(﹣20+5)+(3﹣7)+(7.2+4.8) =﹣15+(﹣4)+12 =﹣7 ② = = = = = ③ = = = ④(﹣1)3×(﹣5)÷[(﹣3)2+2×(﹣5)] =﹣1×(﹣5)÷(9﹣10) =5÷(﹣1) =﹣5 ⑤3.34×(﹣22)+5.84×|﹣4|. =3.34×(﹣4)+5.84×4﹣ =(﹣3.34+5.84)×4﹣4 =6 |