②（3x-4)(x+2)-(x+5)(x-3)
=3x²+2x-8-x²-2x+15
=2x²+7
③(2a-3b)²-(-b+3a)(-3a-b)-
=4a²-12ab+9b²-3ab-b²+9a²+3ab)
=13a²-12ab+8b²
②(a²+1)²-4a²
=(a²+1+2a)(a²+1-2a)
=(a+1)²(a-1)²
③(m+n)³+2m(m+n)²+m²(m+n)
=(m+n)[(m+n)²+2m(m+n)+m²]
=(m+n)((m+n+m)²
=(m+n)(2m+n)²
②（3x-4)(x+2)-(x+5)(x-3)
=3x²+2x-8-x²-2x+15
=2x²+7
③(2a-3b)²-(-b+3a)(-3a-b)-
=4a²-12ab+9b²-3ab-b²+9a²+3ab)
=13a²-12ab+8b²
②(a²+1)²-4a²
=(a²+1+2a)(a²+1-2a)
=(a+1)²(a-1)²
③(m+n)³+2m(m+n)²+m²(m+n)
=(m+n)[(m+n)²+2m(m+n)+m²]
=(m+n)((m+n+m)²
=(m+n)(2m+n)²