Question

-x (ao quadrado)+7x -10 =0

Answer 1

- x² + 7x - 10 = 0

a = -1
b = 7
c = -10

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Delta vale  3 
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As raizes sao  -2 e -5 
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Answer 2

-x² + 7x - 10 = 0
a = -1
b = 7
c = -10
Δ = 7² - (4 * (-1) * (-10) = 49 - 40 = 9
$x = \frac{-7 \pm \sqrt{9} }{2 * (-1)} = \frac{-7 \pm3 }{-2}$
Logo 
$x_{1} = \frac{-7 + 3}{-2} = \frac{-4}{-2} = 2 \\ e\\x_{2} = \frac{-7-3}{-2} = \frac{-10}{-2} = 5$