L'énoncé te donne : (a-b)² = a²-2ab+b²
donc:
1) (x-y)² = x²-2xy+y²
2) (9-x)² = 9²-2*9*x+x² = 81-18x+x²
3) (a-7)² = a²-2*a*7+7² = a²-14a+49
4) (3x-y)² = (3x)²-2*3x*y+y² = 9x²-6xy+y²
5) (a-5b)² = a²-2*a*5b+(5b)² = a²-10ab+25b²
6) (a-2/3)² = a² - 2*a*2/3 + (2/3)² = a² - 4a/3 + 4/9
tu essayes de continuer ?