(1)x²+4＝0→x²-(2i)²＝0→(x+2i)(x-2i)∴x1＝2i,x2＝-2i.(2)x²-2x+3＝0→(x²-2x+1)+2＝0→(x-1)²-(√2i)²＝0→(x-1+√2i)(x-1-√2i)＝0∴x1＝1-√2i,x2＝1+√2i....