5x - 4(6x - x)(x + 3) = (4 - 2x)(3 - 2x) + 2
\(\Leftrightarrow\) 5x - 4.5x(x + 3) = 12 - 8x - 6x + 4x2 + 2
\(\Leftrightarrow\) 5x - 20x2 - 60x = 12 - 8x - 6x + 4x2 + 2
\(\Leftrightarrow\) - 20x2 - 55x = 12 - 14x + 4x2 + 2
\(\Leftrightarrow\) - 20x2 - 4x2 - 55x + 14x = 14
\(\Leftrightarrow\) - 24x2 - 41x = 14
\(\Leftrightarrow\) -24x2 - 41x - 14 = 0
\(\Leftrightarrow\) -(24x2 + 41x + 14) = 0
\(\Leftrightarrow\) 24x2 + 41x + 14 = 0
\(\Leftrightarrow\) 25x2 + 40x + 16 - x2 + x - 2 = 0
\(\Leftrightarrow\) (25x2 + 40x + 16) - (x2 - x + 2) = 0
\(\Leftrightarrow\) (5x + 4)2 = x2 - x + 2
\(\Leftrightarrow\) 5x + 4 = \(\sqrt{x^2-x+2}\)
Mình chịu rồi, nghĩ mãi ko ra
Đáp án là: S = {\(\frac{-41+\sqrt{337}}{48}\); \(\frac{-41-\sqrt{337}}{48}\)}
Chúc bn học tốt!!
