Question

determine o valor de a-2b

Answer 1

$x^{2} + 1 = \frac{5}{2} x$

$x^{2} - \frac{5}{2} x + 1 = 0$

a = 1

b = $- \frac{5}{2}$

c = 1

Δ = b² - 4 . a . c
Δ = $(-\frac{5}{2})^{2} - 4 . 1 . 1$
Δ = $\frac{25}{4} - 4$
Δ = $\frac{25 - 16}{4}$
Δ = $\frac{9}{4}$

$x = \frac{- b (+ ou-) \sqrt{delta} }{2 . a}$

$x = \frac{- (- \frac{5}{2}) (+ ou-) \sqrt{ \frac{9}{4} } }{2 . 1}$

$x = \frac{\frac{5}{2} (+ ou-) { \frac{3}{2} } }{2}$

$x' = \frac{\frac{5}{2} + { \frac{3}{2} } }{2}$

$x' = \frac{\frac{5 + 3}{2} }{2}$

$x' = \frac{\frac{8}{2} }{2}$

$x' = \frac{4} }{2}$

x' = 2

$x" = \frac{\frac{5}{2} - { \frac{3}{2} } }{2}$

$x" = \frac{\frac{5 - 3}{2} }{2}$

$x" = \frac{\frac{2}{2} }{2}$

$x" = \frac{1 }{2}$

a = 2
b = $\frac{1 }{2}$

a - 2b =
2 - $2 . \frac{1 }{2}$ =

2 - $\frac{2 }{2}$ =
2 - 1 =
1

Logo, a - 2b = 1.

Espero ter ajudado
Bons estudos