Nếu \(\int\limits_2^5 {f\left( x \right){\rm{d}}x} = 3\), \(\int\limits_5^7 {f\left( x \right){\rm{d}}x} = 9\) thì \(\int\limits_2^7 {f\left( x \right){\rm{d}}x} \) bằng

Câu hỏi :

Nếu \(\int\limits_2^5 {f\left( x \right){\rm{d}}x}  = 3\) và \(\int\limits_5^7 {f\left( x \right){\rm{d}}x}  = 9\) thì \(\int\limits_2^7 {f\left( x \right){\rm{d}}x} \) bằng bao nhiêu?