已知:x+y=3,xy=-2,求:1.(3x-4y+2xy)-(2x-5y+5xy)的值;2.(3x-5y+4xy)-(6x-2y+6xy)的值
问题描述:
已知:x+y=3,xy=-2,求:1.(3x-4y+2xy)-(2x-5y+5xy)的值;2.(3x-5y+4xy)-(6x-2y+6xy)的值
答
1.(3x-4y+2xy)-(2x-5y+5xy)=3X-4Y+2XY-2X+5Y-5XY=X+Y-3XY∵x+y=3,xy=-2∴X+Y-3XY=3-3×﹙-2﹚=92.(3x-5y+4xy)-(6x-2y+6xy)=3x-5y+4xy-6x+2y-6xy=-3X-3Y-2XY=-3(X+Y)-2XY∵x+y=3,xy=-2∴-3(X+Y)-2XY=-3×3-2×...