Question

Gấp ạ!!!

Answer 1

\(a,f\left(0\right)=0^2+1=1\\ f\left(\dfrac{2}{5}\right)=\left(\dfrac{2}{5}\right)^2-1=\dfrac{4}{25}-1=-\dfrac{21}{25}\\ f\left(-3\right)=\left(-3\right)^2-1=8\)

\(b,f\left(x\right)=x^2-1=3\\ \Leftrightarrow x^2=4\Leftrightarrow x=\pm2\\ f\left(x\right)=x^2-1=35\\ \Leftrightarrow x^2=36\Leftrightarrow x=\pm6\)

Answer 2

b: Ta có: f(x)=3

\(\Leftrightarrow x^2-1=3\)

\(\Leftrightarrow x^2=4\)

hay \(x\in\left\{2;-2\right\}\)

Ta có: f(x)=35

\(\Leftrightarrow x^2-1=35\)

\(\Leftrightarrow x^2=36\)

hay \(x\in\left\{6;-6\right\}\)