Verified answer

1)

x*(x + 1) = 72

x² + x - 72 = 0

delta

d² = 1 + 288 = 289

d = 17

x1 = (-1 + 17)/2 = 8

2)

x² + (x + 1)² = 25

x² + x² + 2x + 1 = 25

2x² + 2x - 24 = 0

x² + x - 12 = 0

delta

d² = 1 + 48 = 49

d = 7

x = (-1 + 7)/2 = 3

3)

x*(x + 1) = 12

x² + x - 12 = 0

delta

d² = 1 + 48 = 49

d = 7

x = (-1 + 7)/2 = 3

4)

x² + (x + 1)² = 85

x² + x² + 2x + 1 = 85

2x² + 2x - 84 = 0

x² + x - 42 = 0

delta

d² = 1 + 168 = 169

d = 13

x = (-1 + 13)/2 = 6

pronto

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