\(a.\)
Theo đề , ta có : \(y=f\left(x\right)=4x^2-5\)
\(\Rightarrow\)
\(f\left(3\right)=4.\left(3\right)^2-5=31\)
\(f\left(-\frac{1}{2}\right)=4.\left(-\frac{1}{2}\right)^2-5=-4\)
\(b.\)
Ta có : \(f\left(x\right)=-1\)
\(\Rightarrow4x^2-5=-1\)
\(\Rightarrow4x^2=-1+5=4\)
\(\Rightarrow x^2=4:4=1\)
\(\Rightarrow x=\sqrt{1}=1\)
\(c.\)
Ta có :
\(f\left(x\right)=4x^2-5\)
\(\Rightarrow f\left(x\right)=4.\left(x\right)^2-5\) \(\left(1\right)\)
\(f\left(-x\right)=4.\left(-x\right)^2-5=4.\left(x\right)^2-5\) \(\left(2\right)\)
Từ \(\left(1\right)\) và \(\left(2\right)\Rightarrow f\left(x\right)=f\left(-x\right)\)
