Cho hai hàm số : \(f\left(x\right)=x^2\) và \(g\left(x\right)=3-x\)
a) Tính \(f\left(-3\right)\), \(f\left(-\dfrac{1}{2}\right)\), \(f\left(0\right)\), \(g\left(1\right)\), \(g\left(2\right)\), \(g\left(3\right)\)
b) xác định a để \(2f\left(a\right)=g\left(a\right)\)
Lời giải:
a)
\(f(-3)=(-3)^2=9; f(-\frac{1}{2})=(\frac{-1}{2})^2=\frac{1}{4}\)
\(f(0)=0^2=0\)
\(g(1)=3-1=2; g(2)=3-2=1; g(3)=3-3=0\)
b)
\(2f(a)=g(a)\)
\(\Leftrightarrow 2a^2=3-a\)
\(\Leftrightarrow 2a^2+a-3=0\Leftrightarrow (2a+3)(a-1)=0\)
\(\Rightarrow \left[\begin{matrix} a=\frac{-3}{2}\\ a=1\end{matrix}\right.\)