[Toán 10] tim m?

L

lequan19942011

theo viet ta co
x1+x2+x3 = m+1
x1x2+x2x3+x3x1=2m
\Rightarrow {x1+x2+x3}^2=x1^2+x2^2+x3^2+2{x1x2+x2x3+x3x1}={m+1}^2
\Leftrightarrow 9+4m=m^2+2m+1
\Leftrightarrow m^2-2m-8=0\Leftrightarrow m=4 hoac m=-2
:)
 
You must log in or register to reply here.
Top Bottom