Sagot :
bonjour
( x + 12 )² = x² + 24 x + 144
( 3 x + 1 ) ( 3 x - 1 ) = 9 x² - 1
( 6 - x )² = 36 - 12 x + x²
( x + 1 )² + ( x - 2 )²
= x² +2 x + 1 + x² - 4 x + 4
= 2 x² - 2 x + 5
Rappel:
(a+b)²=a²+2ab+b²
(a-b)²=a²-2ab+b²
(a+b)(a-b)=a²-b²
a) (x + 12)²
= x²+24x+144
b)(3x+1)(3x-1)
= 9x²-1
c)(6-x)²
=36-12x+x²
=x²-12x+36
d)(x+1)²+(x-2)²
= x²+2x+1+x²-4x+4 On réduit
= 2x²-2x+5
Et voilà! ;)