DFfor.NET.\r3IJ3K@NECD=NA\r(2)3LMKNOPQMKNRKQSTPUNB=NACB=72VWXKQSTP\rUNBEC=NA+NECD=72°,YZNBEC=NB,[UBC=CE0@.\r??`\n`(1)TDE>?@:AC,\r.*.CE=AE,\r...NECD=NA=36°\r(2)VAB=AC,NA=36°,\r.*.ZB=ZACB=72",\rAZBEC=ZA+ZECD=72",\r.,.ZBEC=ZB,\r/.BC=EC=1.\r?!\r\%&<=>?@:<ST3LMKN+OPMKN+RKQST+,-]\r<=>?@:<A+2<=B^C+DEF3*\r257-b(.2a-2\r?:;\n`abc-efg-hi@ac:`bc.\r??`\n`4ab2-4a2b-b'\r=-b(4a2-4ab+b2)\r=-b(2a-b)2.\r?!\r\%&`abcjacj:`bc`kabcHg-hi@aclm'*:\r`]:`$no.\r267(1)12xy+10y2(2)x(x+3)(x-3).\r?:;\n(1)?pg-hi@Qacqr@sactulZvwU\rx8\r(2)Wyz`kabcx,fg-@sac:`bc0@.\r??`\n`:(1)(2x+3y)2-(2x+y)(2x-y)\r=(4x2+12xy+9y2)-(4x2-y2)\r=4x2+12xy+9y2-4x2+y2\r=12xy+10y2\r(2)x3-9xEvaluationWarning:ThedocumentwascreatedwithSpire.PDFfor.NET.\r=x(x2-9)\r=x(x+3)(x-3)\r?!\r\#$%&|c+}jqr`kabcj7acj:`bc~,-ac0`.\r/.