\(\frac{\left(2x+1\right)^2}{5}-\frac{\left(x-1\right)^2}{3}< \frac{7x^2-14x-5}{15}\)
\(\Leftrightarrow\frac{3\left(2x+1\right)^2}{15}-\frac{5\left(x-1\right)^2}{15}< \frac{7x^2-14x-5}{15}\)
\(\Rightarrow3\left(2x+1\right)^2-5\left(x-1\right)^2< 7x^2-14x-5\)
\(\Leftrightarrow3\left(4x^2+4x+1\right)-5\left(x^2-2x+1\right)< 7x^2-14x-5\)
\(\Leftrightarrow\left(12x^2+12x+3\right)-\left(5x^2-10x+5\right)< 7x^2-14x-5\)
\(\Leftrightarrow12x^2+12x+3-5x^2+10x-5< 7x^2-14x-5\)
\(\Leftrightarrow7x^2+22x-2< 7x^2-14x-5\)
\(\Leftrightarrow7x^2+22x-2-7x^2+14x+5< 0\)
\(\Leftrightarrow36x+3< 0\)
\(\Leftrightarrow36x< -3\)
\(\Leftrightarrow x< -\frac{3}{36}\)
\(\Leftrightarrow x< -\frac{1}{12}\)
bn ơi kl phải là <=>x >\(-\frac{1}{12}\)
