Question

若多项式x²-3kxy-3y²-1/4xy-1 合并同类项后不含xy项 求k的值

Answer 1

x²-3kxy -3y²-1/4xy -1

=x²-3y²- 3kxy -1/4xy -1

=x²-3y²-(3k-1/4)xy -1

因为不含xy项,所以xy的系数为0

所以3k-1/4=0

3k=1/4

k=1/4 ÷3

k=1/12