Câu 14:
a: Đúng
b: \(f\left(-\Omega\right)=sin^2\left(-\Omega\right)+cos\left(-\Omega\right)-1=0+\left(-1\right)-1=-2\)
\(-f\left(\Omega\right)=-\left[sin^2\left(\Omega\right)+cos\left(\Omega\right)-1\right]=-\left[0+\left(-1\right)-1\right]=2\)
=>Sai
c: \(f\left(-x\right)=sin^2\left(-x\right)+cos\left(-x\right)-1=sin^2x+cosx-1=f\left(x\right)\)
=>Đúng
d: Đúng
Câu 11:
tan 3x-tan x=0
=>tan 3x=tan x
=>\(\left\{{}\begin{matrix}3x=x+k\Omega\\3x\ne\dfrac{\Omega}{2}+k\Omega\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x=k\Omega\\x\ne\dfrac{\Omega}{6}+\dfrac{k\Omega}{3}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{k\Omega}{2}\\x\ne\dfrac{\Omega}{6}+\dfrac{k\Omega}{3}\end{matrix}\right.\)
=>\(x=k\Omega\)
\(x\in[0;2\Omega)\)
=>\(k\Omega\in[0;2\Omega)\)
=>\(k\in[0;2)\)
=>\(k\in\left\{0;1\right\}\)
=>Có 2 nghiệm
=>Chọn C
