Question

giúp em vs

Answer 1

e:=>3x(x^2-25)=0

=>x(x-5)(x+5)=0

hay \(x\in\left\{0;5;-5\right\}\)

b:Δ=2^2-4*2*(-15)=4+120=124>0

=>PT có hai nghiệm pb là:

\(\left\{{}\begin{matrix}x_1=\dfrac{-2-2\sqrt{31}}{4}=\dfrac{-1-\sqrt{31}}{2}\\x_2=\dfrac{-1+\sqrt{31}}{2}\end{matrix}\right.\)

Answer 2

e)

\(3x^3-75x=0\\ 3x\left(x^2-25\right)=0\\ 3x\left(x-5\right)\left(x+5\right)=0\\ \left[{}\begin{matrix}3x=0\\x-5=0\\x+5=0\end{matrix}\right.\left[{}\begin{matrix}x=0\\x=5\\x=-5\end{matrix}\right.\)

l)

\(2x^2+2x-15=0\)

câu này xem lại đề nhé