20-2D+4E+F＝0 10+3D-E+F＝0.D∧2-4F＝36 求D.E.F
问题描述：
20-2D+4E+F＝0 10+3D-E+F＝0.D∧2-4F＝36 求D.E.F
答
20-2D+4E+F＝0 ① 10+3D-E+F＝0.②D∧2-4F＝36 ③① +②*4：60+10D+5F=0,得12+2D+F=0 ④③+④*4:D^2+48+8D=36,得D^2+8D+12=0,（D+2)(D+6)=0,得D=-2或-6当D=-2时,由④,得F=-2D-12=4-12=-8,由 ②,E=10+3D+F=10-6-8=-4....