[질문] 사차방정식근과계수의관계알려주세요

4차항의계수를a라하고,네근을b,c,d,e라하면a(x-b)(x-c)(x-d)(x-e)=0이것을전개하면ax^4-a(b+c+d+e)x^3+a(bc+bd+be+cd+ce+de)x^2-a(bde+cde+bcd+bce)x+abcde=0