解:(扮梁1) 2(2a²+9b)判游+3(-5a²-4b)
=4a²+掘缺销18b-15a²-12b
=-11a²+6b
(2) -3(2x²-xy)+4(x²+xy-6)
=-6x²+3xy+4x²+4xy-24
=-2x²+7xy-24
2(罩羡2a2+9b)兆脊+3(物猜拍-5a2-4b)
=4a2+18b+ (-15a2-12b)
=(4-15)a2+(18-12)b
=-11a2+6b
-3(2x2-xy)+4(x2+xy-6)
=-6x2+3xy+4x2+4xy-24
=-2x2+7xy-24