(2x - 1)^2 + (x + 3)^2 - 5(x + 7)(x - 7) = 0
<=>4x^2-4x+1+x^2+6x+9-5x^2+245=0
<=>2x+255=0
<=>2x=-255
<=>x=-255/2
Có trên google ( ghi nguồn đầy đủ )
\(\left(2x-1\right)^2+\left(x+3\right)^2-5\left(x+7\right)\left(x-7\right)=0\)
\(\Leftrightarrow\)\(4x^2-4x+1+x^2+6x+9-5\left(x^2-49\right)=0\)
\(\Leftrightarrow\)\(5x^2+2x+10-5x^2+245=0\)
\(\Leftrightarrow\)\(2x=-255\)
\(\Leftrightarrow\)\(x=-127,5\)
Vậy...
4x^2 - 2.2x.1 + 1^2 + x^2 + 2.x.3 + 3^2 - 5.x^2 + 5. 7^2 = 0
4x^2 - 4x + 1 + x^2 + 6x + 9 - 5x^2 + 245 = 0
2x + 1 + 9 + 245 = 0
=> x = 127,5
\(\left(2x-1\right)^2+\left(x+3\right)^2-5\left(x+7\right)\left(x-7\right)=0\)
\(=4x^2-4x+1+\left(x+3\right)^2-5\left(x+7\right)\left(x-7\right)\)
\(=4x^2-4x+1+x^2+6x+9-5x^2+245\)
\(\Rightarrow x=-\frac{255}{2}\left(=-127.5\right)\)