`a, <=> 4x^2 - 3x - 10 - 4x^2 - 12x - 9 = 6`
`<=> -15x -25 = 0`
`<=> x = -5/3`
`b, 20x - 15x^2 - 3x + 4 =0`
`<=> -15x^2 + 17x + 4 = 0``
`=>` \(\left[{}\begin{matrix}x=\dfrac{4}{3}\\x=-\dfrac{1}{5}\end{matrix}\right.\)
a: \(\Leftrightarrow4x^2-8x+5x-10-4x^2-12x-9=6\)
=>-15x-19=6
=>-15x=25
hay x=-5/3
b: \(\Leftrightarrow\left(4-3x\right)\left(5x+1\right)=0\)
=>x=4/3 hoặc x=-1/5