Question

calcule ( x + 7) . ( x + 5 )

Answer 1

x.x+x.5+7.x+7.5
x2 + 5x+7x + 35
x2 +12x+ 35

Answer 2

$( x+7) . ( x + 5)$   
x.x + 5x + 7x + 7.5
x² + 5x + 7x + 35
x² + 12x + 35 = 0

 $b^2 - 4 . a . c$
12² - 4 . 1. 35
144 - 140 = 4

- 12 +- √4 / 2  = -12 + 2 / 2 = -5
                     = -12 - 2 / 2 = +7
                     R = -5,-7