Question

Cho hàm số xác đinh \(f\left(x\right)=x^2-5x+6\)

Tính \(f\left(2\right);f\left(3\right)\)

Xác định x để \(f\left(x\right)=6\)

Answer 1

a) Xác đinh \(f\left(2\right);f\left(3\right)\)

\(f\left(x\right)=x^2-5x+6\)
\(f\left(x\right)=x^2-2x-3x+6\)

\(f\left(x\right)=x\left(x-2\right)-3\left(x-2\right)\)
\(f\left(x\right)=\left(x-2\right)\left(x-3\right)\)
\(f\left(2\right)=f\left(3\right)=0\)

b) Tìm x f(x) =6

\(f\left(x\right)=6\Rightarrow x^2-5x+6=6\)
\(\Leftrightarrow x^2-5x=0\)

\(\Rightarrow x\left(x-5\right)=0\)
\(\Rightarrow x=0\\ x=5\)