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- #### \( a = 3, b = -12, c = 9 \)
- #### \( rac{3}{5}\)1.
- \[ S = 15 imes (15 + 1) = 15 imes 16 = 240 \]
- \[ b^2 - 4ac = (-5)^2 - 4 imes 2 imes (-3) = 25 + 24 = 49 \]
- \[ x = rac{-(-5) \pm \sqrt{49}}{2 imes 2} = rac{5 \pm 7}{4} \]
- \[ x = rac{5 + 7}{4} = 3 \quad ext{and} \quad x = rac{5 - 7}{4} = - rac{1}{2} \]
