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)(...