Question

k cần giải chi tiết đâu ạ

 

Answer 1

\(B=\left(3a-\dfrac{1}{2}\right)xy^4z^2\cdot\left(xy^2\right)^3+\left(a-1\right)\cdot y^2z^2\cdot\left(xy^2\right)^4\)

\(=\left(3a-\dfrac{1}{2}\right)\cdot xy^4z^2\cdot x^3y^6+\left(a-1\right)\cdot y^2z^2\cdot x^4y^8\)

\(=\left(3a-\dfrac{1}{2}\right)\cdot x^4y^{10}z^2+\left(a-1\right)\cdot x^4y^{10}z^2\)

\(=\left(3a-\dfrac{1}{2}+a-1\right)\cdot x^4y^{10}z^2\)

\(=\left(4a-\dfrac{3}{2}\right)\cdot x^4y^{10}z^2\)

Để B<0 thì \(4a-\dfrac{3}{2}< 0\)

=>\(4a< \dfrac{3}{2}\)

=>\(a< \dfrac{3}{2}:4=\dfrac{3}{8}\)