Answer: a) [tex]x=\dfrac{-9 \pm\sqrt{113} }{8}[/tex]
b) x₁ = - 14; x₂ = 6.
Step-by-step explanation:
a) 4x² + 9x - 2 = 0
[tex]x=\dfrac{-b \pm \sqrt{b^{2}-4ac } }{2a} \\\\a=4; \: \: b=9; \: \: c=-2\\x =\dfrac{-9 \pm \sqrt{9^{2}-4 \cdot 4 \cdot (-2) } }{2 \cdot 4} =\dfrac{-9 \pm\sqrt{113} }{8}[/tex]
b) x² + 8x - 84 = 0
[tex]x=\dfrac{-b \pm \sqrt{b^{2}-4ac } }{2a} \\\\a=1; \: \: b=8; \: \: c=-84\\\\x =\dfrac{-8 \pm \sqrt{8^{2}-4 \cdot 1 \cdot (-84) } }{2 \cdot 1} =\dfrac{-8 \pm\sqrt{400} }{2}=\dfrac{-8 \pm 20}{2} =-4 \pm 10\\\\x_{1} =-14\\x_{2} =6[/tex]
