\(A=\left(x+a\right)\left(x+b\right)\left(x+c\right)\)
\(=\left(x^2+ax+bx+ab\right)\left(x+c\right)\)
\(=x^3+ax^2+bx^2+abx+cx^2+acx+bcx+abc\)
\(=x^3+\left(a+b+c\right)x^2+\left(ab+bc+ca\right)x+abc\)
Theo bài ra ta có:
\(a+b+c=6\)
\(ab+bc+ca=-7\)
\(abc=-60\)
\(\Rightarrow A=x^3+6x^2-7x-60\)