若a²+2b²-7=0,求：

（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