bonjour
P a = x ( 5 x + 3 )
= 5 x² + 3 x
4/7
5 * 4/7 = 20/7
20/7 + 3 = ( 20 + 21) / 7 = 41 /7
41/7 x 4/7
= 164/49
P B
5 ( x² - 6) = 5 x² - 30
4/7
( 4/7)² = 16/49
16/49 - 6 = ( 16/49 - 294/49 ) = - 278/49
- 278/49 * 5
= - 1390 /49
5 x ² + 3 x = 5 x² - 30
5 x² - 5 x² + 3 x = - 30
3 x = - 30
x = - 10
il faut choisir - 10
2 ( 2 x + 3 + 3 x + 1 )
= 4 x + 6 + 6 x + 2
= 10 x + 8
10 x + 8 = 28
10 x = 20
x = 2
si x = 2
2 x +3 = 7
3 x + 1 = 7
donc est un carré
