(a-3b)(a+2b)+5a(a+2b)

( a - 3b )( a + 2b ) + 5a ( a + 2b ) = ( a + 2b )( a - 3b + 5a ) = ( a + 2b )( 6a -3b ) = 6a^2 - 3ab + 12ab - 6b^2 = 6a^2 - 6b^2 + 9ab

a2+2ab-3ab-6b2+5a2+10ab=6a2+9ab-6b2