Bjr,
a.
[tex]3x^2 - 5x + 2 = 12 - 2 (x-2)^2\\3x^2-5x+2=12-2(x^2-2\times x \times 2 + 2^2)\\3x^2-5x+2=12-2(x^2-4x+4)\\3x^2-5x+2=12-2x^2+8x-8\\3x^2-5x+2=4-2x^2+8x\\3x^2-5x+2-4+2x^2-8x=0\\\boxed{5x^2-13x-2=0}\\\\\Delta = b^2-4ac\\\Delta = (-13)^2-4\times 5 \times (-2)\\\Delta = 169 + 40\\\Delta = 209\\\\x_1 = \dfrac{-b-\sqrt{\Delta}}{2a}\\\\x_1 = \dfrac{-(-13)-\sqrt{209}}{2\times 5}\\\\x_1 = \dfrac{-(13-\sqrt{209}}{10}\\\\x_2 = \dfrac{-b+\sqrt{\Delta}}{2a}\\\\x_2 = \dfrac{13+\sqrt{209}}{10}\\\\\\\\\text{S}=\left\{\dfrac{13-\sqrt{209}}{10}; \dfrac{13+\sqrt{209}}{10}\right\}\\\\[/tex]
b.
[tex]3a - 7 = 9a + 2\\
3a-9a = 7+2\\
-6a = 9\\\\
-a = \dfrac{9}{6}\\\\
a = -\dfrac{9}{6}\\\\
a = -\dfrac{3}{2}\\\\[/tex]
