Cc Svp je n’arrive pas à comprendre aidez moi merci beaucoup

Bonsoir,

(x+1)² = (x-2)² + 2²

x² +2x +1 = x²-4x +4 +4

x²-x² +2x  +4x  =8-1

6x =7

x= 7/6

10² = (x+1)² +(x-1)²

100 = x² +2x +1 +x² -2x +1

100 = 2x² +2

100 = 2(x²+1)

100/2 = x² +1

50 -1 = x²

49 = x²

x= 7