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a)
$3x^2-4x-4=0$
$x=\frac{4\pm\sqrt{\left(-4\right)^2-4\cdot3\cdot\left(-4\right)}}{2\cdot3}=\frac{4\pm\sqrt{16+3\cdot16}}{6}=\frac{4\pm\sqrt{64}}{6}=\frac{4+8}{6}=\frac{12}{6}=2\ tai\ \frac{4-8}{6}=-\frac{4}{6}=-\frac{2}{3}$
b)

c)
$-\frac{2}{3}\le x\le2{,}\ x\ on\ välillä\ \left[-\frac{2}{3}{,}\ 2\right]$