若a,b满足丨a+0.7丨+丨b-0.49丨=0,求多项式3a?+4b-2a?-5b的值,
问题描述:
若a,b满足丨a+0.7丨+丨b-0.49丨=0,求多项式3a?+4b-2a?-5b的值,
答
a+0.7=0
b-0.49=0
∴a=-0.7
b=0.49
3a²+4b-2a²-5b
=a²-b
=0.49-0.49
=0