國二數學五題？急！

1.
(2/5) - (x²/2) = 0
x²/2 = 2/5
x² = 4/5
x = √(4/5) 或 x = -√(4/5)
x = 2/√5 或 x = -2/√5
x = (2/5)√5 或 x = -(2/5)√5


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2.
9(x + 2)² - 8 = 0
9(x + 2)² = 8
(x + 2)² = 8/9
(x + 2) = √(8/9) 或 (x + 2) =-√(8/9)
x + 2 = 2(√2)/3 或 x + 2 = -2(√2)/3
x = -2 + [2(√2)/3] 或x = -2 - [2(√2)/3]


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3.
(2x + 19)² - 3 = 0
(2x + 19)² = 3
2x + 19 = √3 或 2x + 19 = -√3
2x = -19 + √3 或2x = -19 - √3
x = (-19 + √3)/2 或 x = (-19 - √3)/2


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4.
4(x + 5)² = 7
(x + 5)² = 7/4
x + 5 = √(7/4) 或 x + 5 = -√(7/4)
x + 5 = √(7)/2 或 x + 5 = -√(7)/2
x = -5 + [√(7)/2] 或 x = -5 - [√(7)/2]


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5.
(5x²/2) - 3x = 0
2[(5x²/2) - 3x] = 0
5x² - 6x = 0
x(5x - 6) = 0
x = 0 或 x = 6/5

1. 正負 5分之4根號
2.2-3分之2根號2 和 2+3分之2根號2
3.2分之19+根號2 和2分19-根號3
4.5加減2分之根號7
5.0或5分之6

有錯抱歉
很久沒算數學了