Question

 Xác định hệ số a,b,c biết : (2x-5) . (3x+b) = ax^2+x+c

Answer 1

\( \left(2x-5\right)\left(3x+b\right)=ax^2+x+c\)

\(\Rightarrow2x\left(3x+b\right)-5\left(3x+b\right)=ax^2+x+c\)

\(\Rightarrow6x^2+2bx-15x-5b=ax^2+x+c\)

\(\)\(\Rightarrow6x^2+\left(2b-15\right)x-5b=ax^2+x+c\)

\(\Rightarrow\hept{\begin{cases}6x^2=ax^2\\\left(2b-15\right)x=x\\-5b=c\end{cases}\Rightarrow\hept{\begin{cases}a=6\\2b-15=1\\-5b=c\end{cases}\Rightarrow}}\hept{\begin{cases}a=6\\b=8\\c=-40\end{cases}}\)