Question

0.38*7+19/50+4*19/50简便怎么计算

帮帮忙。知道的+qq534426202

Answer 1

0.38*7+19/50+4*19/50
=0.38*7+(1+4)*19/50
=0.38*7+5*19/50
=0.38*7+19/10
=0.19*2*7+1.9
=0.19*14+0.19*10
=0.19*(14+10)
=0.19*14
=2.66

Answer 2

-π/2＜a＜π/2
-π/2＜b＜π/2
相加
-π＜a+b＜π

-π/2＜b＜π/2
所以-π/2＜-b＜π/2
-π/2＜a＜π/2
相加
-π＜a-b＜π
a＜b
所以a-b＜0
所以-π＜a-b＜0