Question

两道数学题啊！！！！！ 帮个忙~~~

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

Answer 1

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

(2)=-2(a²+2b²)+1
=-2(a²+2b²-7+7)+1
=-2(a²+2b²-7)-14+1
=-2*0-13
=-13

Answer 2

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

Answer 3

（1)=a²+2b²-3-4+4
=(a²+2b²-7)+4
=4

(2)=-2(a²+2b²)+1
=-2(a²+2b²-7+7)+1
=-2(a²+2b²-7)-14+1
=-2*0-13
=-13

Answer 4

第（1）值为4，第（2）值为-13