(2x+3)(5x-4)=10x^2+15x-8x-12=10x^2+7x-12
(3a-2)(2a-1)=6a^2-4a-3a+2=6a^2-7a+2
(5a-3b)(4a-b)=20a^2-12ab-5ab+3b^2=20a^2-17ab+3b^2
(3x+2y)(x-y)=3x^2+2xy-3xy-2y^2=3x^2-xy-2y^2
(5b-4c)(2b-2c)=10b^2-8bc-10bc+8c^2=10b^2-18bc+8c^2
(p-3q)(8p+5q)=8p^2-24pq+5pq-15q^2=8p^2-19pq-15q^2