Question

tìm x sao cho (x^2-20)(x^2-15)(x^2-10)(x^2-5)<0

Answer 1

\(^{\left(x^2-20\right)\left(x^2-15\right)\left(x^2-10\right)\left(x^2-5\right)< 0}\)

=>\(x^2\left(1-20-15-10-5\right)< 0\)

=>\(^{x^2.\left(-49\right)< 0}\)

=>x²<49

=>x\(\in\)(\(\orbr{\begin{cases}1\\-1\end{cases}}\)\(,\orbr{\begin{cases}2\\-2\end{cases}},\orbr{\begin{cases}3\\-3\end{cases}},\orbr{\begin{cases}4\\-4\end{cases}},\orbr{\begin{cases}5\\-5\end{cases}},\orbr{\begin{cases}6\\-6\end{cases}}\))

Vì x<0=>x\(\in\)(-1,-2,-3,-4,-5,-6)

tk mình nhé