原式=9a²-12ab+4b²-2a²-ab+6ab+3b²+9a²-3ab+3ab-b²
=16a²-7ab+6b²
由已知得:a=3,-3 b=4
原式=16X3²-7X3X4+6X4²
=144-84+96
=156
或=16X3²-7X(-3)X4+6X4²
=144+84+96
=324
原式=9a²-12ab+4b²-2a²-ab+6ab+3b²+9a²-3ab+3ab-b²
=16a²-7ab+6b²
由已知得:a=3,-3 b=4
原式=16X3²-7X3X4+6X4²
=144-84+96
=156
或=16X3²-7X(-3)X4+6X4²
=144+84+96
=324