Question

cate dintre numerele -7;-5;5;7 sant solutii ale ecuatiei x²+2x-1=0

Answer 1

$x^{2} +2x-1=0$

$x= \frac{-2+- \sqrt{2^2-4*1*(-1)} }{2*1}$

$x= \frac{-2+- \sqrt{4+4} }{2}$

$x= \frac{-2+- \sqrt{8} }{2}$

$x= \frac{-2+-2 \sqrt{2} }{2}$

$\left \{ {{x= \frac{-2+2 \sqrt{2} }{y2 } \atop {x= \frac{-2-2 \sqrt{2} }{2} }} \right.$


$x=-1+ \sqrt{2}$

$x=-1- \sqrt{2}$

[tex] x_{1} =-1- \sqrt{2} x_{2} =-1+ \sqrt{2} [/tex]

Answer 2

$x^2+2x-1=0 \\ \\ \Delta = 2^2-4\cdot 1\cdot (-1) = 4+4 =8 \\ \\ Delta nu e patrat perfect \Rightarrow nu avem solutii rationale \Rightarrow \\ \\ \Rightarrow niciunul din -7;-5;5;7 nu e solutie a ecuatiei.$