bonjour

x² - 8 x + 7 = 0

Δ  = ( - 8 )² - 4 ( 1 * 7 ) = 64 - 28 = 36

x 1  = ( 8 - 6 ) / 2 = 2/2 = 1

x 2 =  ( 8 + 6 ) / 2 = 14/2 = 7

2 x² + x - 3  = 0

Δ  = 1 ² - 4 ( 2 * - 3 ) = 1 + 24 = 25

x 1 = (  - 1 - 5 ) / 4 = - 6 /4 = -  3 /2

x 2  = ( - 1 + 5 ) / 4 = - 4 /4 = - 1

bjr

x² - 8x + 7 = 0

x² - x - 7 x + 7 = 0

x ( x - 1 ) - 7 ( x - 1 ) = 0

(x-1)(x-7) = 0

x - 1 = 0 ou x -7 = 0

x = 1 ou x = 7

2x² + x - 3 = 0

x ( 2x + 3 ) - ( 2x + 3 ) = 0

(2x+3)(x - 1) = 0

2x = - 3 ou x = 1

x = -3/2 ou x = 1

bonne journée