Question

c) (x-1)2 – 2(3+x)2 – x 2 = 0

Answer 1

\(\left(x-1\right)^2-2\left(3+x\right)^2-x^2=0\)

\(\Leftrightarrow x^2-2x+1-2\left(9+6x+x^2\right)-x^2=0\)

\(\Leftrightarrow-2x+1-18-12x-2x^2=0\)

\(\Leftrightarrow-2x^2-14x-17=0\)

\(\Leftrightarrow2x^2+14x+17=0\)

Ta có: \(\Delta'=49-34=15>0\) 

Vậy phương trình có 2 nghiệm phân biệt:

\(\left[{}\begin{matrix}x_1=\dfrac{-7+\sqrt{15}}{2}\\x_2=\dfrac{-7-\sqrt{15}}{2}\end{matrix}\right.\)

Answer 2

=(x^2-2x+1)-(6-2x)-x^2

=x^2-2x+1-6-2x-x^2

=-5

Vậy...

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