若a²+2b²-7=0,求:(1)a²+2b²-3的值.(2)-2a²-4b²+1

问题描述:

若a²+2b²-7=0,求:(1)a²+2b²-3的值.(2)-2a²-4b²+1

a²+2b²-7=0
∴a²+2b²=7
(1)a²+2b²-3
=(a²+2b²)-3
=7-3=4
(2)-2a²-4b²+1
=-2(a²+2b²)+1
=-2×7+1
=-13