1
a, 4x2+4x+2
= 2x2+2x2+2x+2x+2
= 2x2+(2x2+2x)+(2x+2)
= 2x2+ 2x(x+1)+2(x+1)
= 2x2+(2x+2)(x+1)
= 2x2+2(x+1)(x+1)
=2x2+2(x+1)2
Để 2x2+2(x+1)2=0
=>\(\left\{{}\begin{matrix}2x^2=0\\2\left(x+1\right)^2=0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}x^2=0\\\left(x+1\right)^2=0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}x=0\\x+1=0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}x=0\\x=-1\end{matrix}\right.\)(vô lý)
=> đa thức 4x2+4x+2 vô nghiệm
1
b, y2+6y+10
= y2+3y+3y+9+1
= y(3+y)+3(y+3)+1
= (y+3)(y+3)+1
= (y+3)2+1
Có (y+3)2\(\ge\)0;1>0
=> (y+3)2+1>0
=> y2+6y+10 vô nghiệm
1
c, y2-4y+5
= y2-2y-2y+4+1
= y(y-2)-2(y-2)+1
= (y-2)(y-2)+1
= (y-2)2+1
mà(y-2)2\(\ge\)0; 1>0
=>(y-2)2+1>0
=>y2-4y+5 vô nghiệm
