Question

Bài 2 :Giaỉ các phương trình sau

a) y(y² -1)=y²-5y+6=0

b)y(y-\(\dfrac{1}{2}\))(2y+5)=0

c)4y²+1=4y

d)y²-2y=80

e)(2y-1)²-(y+3)²=0

f)2y²-11y=0

g)(2y-3)(y+1)+y(y-2)=3(y+2)²

h)(y²-2y+1)-9=0

i)y²+5y+6=0

k) y²+7y+2=o

l)y²-y-12=0

m)x²+2x+7=0

n)y³-y²-21y+45=0

p)2y³-5y²+8y-3=0

q) (y+3)² +(y+5)²=0

Answer 1

c.

\(4y^2+1=4y\)

\(\Leftrightarrow4y^2-4y+1=0\)

\(\Leftrightarrow4y^2-2y-2y+1=0\)

\(\Leftrightarrow2y\left(2y-1\right)-\left(2y-1\right)=0\)

\(\Leftrightarrow\left(2y-1\right)^2=0\)

\(\Leftrightarrow y=0\)

d.

\(y^2-2y=80\)

\(\Leftrightarrow y^2-2y-80=0\)

\(\Leftrightarrow y^2-10y+8y-80=0\)

\(\Leftrightarrow y\left(y-10\right)+8\left(y-10\right)=0\)

\(\Leftrightarrow\left(y+8\right)\left(y-10\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}y+8=0\\y-10=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}y=-8\\y=10\end{matrix}\right.\)