a的平方+2a-8=0
a²+2a=8
a(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
a的平方+2a-8=0
a²+2a=8
a(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