(2a+b)^2-(3a-b)^2+5a(a-b)
=(2a+b+3a-b)(2a+b-3a+b)+5a(a-b)
=5a(-a+2b)+5a(a-b)
=5a(-a+2b+a-b)
=5ab
=5*1/10*1/5
=1/10