a, Thay m = 1 ta đc

\(x^2-1=0\Leftrightarrow x=1;x=-1\)

b, \(\Delta'=\left(m-1\right)^2-\left(2m-3\right)=m^2-4m+4=\left(m-2\right)^2\)

Để pt có 2 nghiệm pb khi delta' > 0 

\(m-2\ne0\Leftrightarrow m\ne2\)

c, để pt có 2 nghiệm trái dấu khi \(x_1x_2=2m-3< 0\Leftrightarrow m< \dfrac{3}{2}\)

d. 

Theo Viet: \(\left\{{}\begin{matrix}x_1+x_2=2m-2\\x_1x_2=2m-3\end{matrix}\right.\)

Trừ vế cho vế:

\(\Rightarrow x_1+x_2-x_1x_2=1\)

Đây là hệ thức liên hệ 2 nghiệm ko phụ thuộc m

a,\(\Delta=\left[-\left(2m+3\right)\right]^2-4m=4m^2+12m+9-4m=4m^2+8m+9\)\(=\)\(4\left(m^2+2m+\dfrac{9}{4}\right)=4\left(m+1\right)^2+5\ge5>0\)

=>pt luôn có 2 nghiệm phân biệt 

b,vi ét \(=>\left\{{}\begin{matrix}x1+x2=2m+3\\x1x2=m\end{matrix}\right.\)

\(T=\left(x1+x2\right)^2-2x1x2=\left(2m+3\right)^2-2m=4m^2+12m+9-2m\)\(=4m^2+10m+9=4\left(m^2+\dfrac{10}{4}m+\dfrac{9}{4}\right)=4\left[\left(m+\dfrac{5}{4}\right)^2+\dfrac{11}{16}\right]\)\(=4\left(m+\dfrac{5}{4}\right)^2+\dfrac{11}{4}\ge\dfrac{11}{4}\)

dấu"=" xảy ra<=>m=-5/4

a: Δ=(-2m)^2-4(m-2)

=4m^2-4m+8=(2m-1)^2+7>=7>0

=>PT luôn có hai nghiệm phân biệt

b: x1^2+x2^2-6x1x2

=(x1+x2)^2-8x1x2

=(2m)^2-8(m-2)

=4m^2-8m+16=(2m-2)^2+8>=8

=>24/(2m-2)^2+8<=3

=>M>=-3

Dấu = xảy ra khi m=1

Hc tốt nha

Mik chuyên toán nên cứ tin mik bảo đảm đúng

1.

\(a+b+c=0\) nên pt luôn có 2 nghiệm

\(\left\{{}\begin{matrix}x_1+x_2=m\\x_1x_2=m-1\end{matrix}\right.\)

\(A=\dfrac{2x_1x_2+3}{x_1^2+x_2^2+2x_1x_2+2}=\dfrac{2x_1x_2+3}{\left(x_1+x_2\right)^2+2}=\dfrac{2\left(m-1\right)+3}{m^2+2}=\dfrac{2m+1}{m^2+2}\)

\(A=\dfrac{m^2+2-\left(m^2-2m+1\right)}{m^2+2}=1-\dfrac{\left(m-1\right)^2}{m^2+2}\le1\)

Dấu "=" xảy ra khi \(m=1\)

2.

\(\Delta=m^2-4\left(m-2\right)=\left(m-2\right)^2+4>0;\forall m\) nên pt luôn có 2 nghiệm pb

Theo Viet: \(\left\{{}\begin{matrix}x_1+x_2=m\\x_1x_2=m-2\end{matrix}\right.\)

\(\dfrac{\left(x_1^2-2\right)\left(x_2^2-2\right)}{\left(x_1-1\right)\left(x_2-1\right)}=4\Rightarrow\dfrac{\left(x_1x_2\right)^2-2\left(x_1^2+x_2^2\right)+4}{x_1x_2-\left(x_1+x_2\right)+1}=4\)

\(\Rightarrow\dfrac{\left(x_1x_2\right)^2-2\left(x_1+x_2\right)^2+4x_1x_2+4}{x_1x_2-\left(x_1+x_2\right)+1}=4\)

\(\Rightarrow\dfrac{\left(m-2\right)^2-2m^2+4\left(m-2\right)+4}{m-2-m+1}=4\)

\(\Rightarrow-m^2=-4\Rightarrow m=\pm2\)