a的平方+2a-8=0a²+2a=8a(a+2)的平方-a(a-3)(a-1)+3(5a-2)=a(a²+4a+4)-a(a²-4a+3)+15a-6=a(a²+4a+4-a²+4a-3)+15a-6=8a²+a+15a-6=8(a²+2a)-6=8×8-6=58