Toán Lớp 8: tìm y biết :
a,(5y^4-3y^3):2y^3= 1/2
b, (y^4-2y^2-8):(y-2)=0
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 8: tìm y biết :
a,(5y^4-3y^3):2y^3= 1/2
b, (y^4-2y^2-8):(y-2)=0
Comments ( 1 )
a)Dkxd:y \ne 0\\
\left( {5{y^4} – 3{y^3}} \right):2{y^3} = \dfrac{1}{2}\\
\Leftrightarrow 5{y^4}:2{y^3} – 3{y^3}:2{y^3} = \dfrac{1}{2}\\
\Leftrightarrow \dfrac{5}{2}y – \dfrac{3}{2} = \dfrac{1}{2}\\
\Leftrightarrow \dfrac{5}{2}y = \dfrac{1}{2} + \dfrac{3}{2} = 2\\
\Leftrightarrow y = 2:\dfrac{5}{2}\\
\Leftrightarrow y = \dfrac{4}{5}\\
Vậy\,y = \dfrac{4}{5}\\
b)Dkxd:y \ne 2\\
\left( {{y^4} – 2{y^2} – 8} \right):\left( {y – 2} \right) = 0\\
\Leftrightarrow {y^4} – 2{y^2} – 8 = 0\\
\Leftrightarrow {y^4} – 4{y^2} + 2{y^2} – 8 = 0\\
\Leftrightarrow \left( {{y^2} – 4} \right)\left( {{y^2} + 2} \right) = 0\\
\Leftrightarrow {y^2} – 4 = 0\left( {{y^2} + 2 > 0} \right)\\
\Leftrightarrow {y^2} = 4\\
\Leftrightarrow y = 2;y = – 2\\
Vậy\,y = 2;y = – 2
\end{array}$