当x=0.5,y=0.9时,求2.5x-2y+5.5x的值先化简再求值

当x=0.5,y=0.9时,求2.5x-2y+5.5x的值先化简再求值
当x=0.5,y=0.9时,求2.5x-2y+5.5x的值
先化简再求值

当x=0.5,y=0.9时,求2.5x-2y+5.5x的值先化简再求值
2.5x-2y+5.5x
=（2.5+5.5）x-2y
=8x-2y
=8×0.5-2×0.9
=4-1.8
=2.2

原式=8x-2y
=4-1.8
=2.2

当x=0.5,y=0.9时，
2.5x-2y+5.5x=2.5*0.5-2*0.9+5.5*0.5
=1.25--1.8+2.75
=1.25+2.75-1.8
=4-1.8
=3.2