1/(x^2-13x+42)+1/(x^2-14x+48)+1/(x^2-15x+56)
问题描述：
1/(x^2-13x+42)+1/(x^2-14x+48)+1/(x^2-15x+56)
答
我建议你用各个击破还有尖子生教材，特别哟创意！ ytt 1)x^2-答案：x1=-10 x2=-9 (15)x^2-25x+156=0 答案：x1=13 x2=12
答
你能告诉我你是要干什么吗？
答
1/(x²-13x+42)+1/(x²-14x+48)+1/(x²-15x+56)=1/[(x-6)(x-7)]+1/[(x-6)(x-8)]+1/[(x-7)(x-8)]=[(x-8)+(x-7)+(x-6)]/[(x-6)(x-7)(x-8)]=(3x-21)/[(x-6)(x-7)(x-8)]=3(x-7)/[(x-6)(x-7)(x-8)]=3/[(x-6)(...