Răspuns:
a) x² = 25
x = radical 25
x = -5
b) x² = 49
x = radical 49
x = -7
c) x² = 144
x = radical 144
x = -12
d) 2x² = 200
x² = 200 : 2
x² = 100
x = radical 100
x = -10
e) x² + 1 = 82
x² = 82 -1
x² = 81
x = radical 81
x = -9
f) x² - 15 = 210
x² = 210 + 15
x² = 225
x = radical 225
x = -15
g) 2x² + 16 = 816
2x² = 816 - 16
2x² = 800
x² = 800 : 2
x² = 400
x = radical 400
x = -20
h) -x² + 5 = -4
-x² = -4 -5
-x² = -9
x² = 9
x = radical 9
x = -3