(2a -7)² - (a+1).(a-1)

4a + 49 - 2a -a + a -1

4a + 49 - 2a -1

4a -2a = -1 -49

2a = -50 (-1)

a = 50/2

a=25

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(x+3)²-(2x-7)²-(x+8).(x+8)

2x + 9 -4x + 49 - 2x + 8x + 8x + 64

2x -4x -2x +8x +8x = -64 -9 -49

10x = -122 (-1)

x= 12.2

x = 122/10

x=12.2