Tìm x: a) \( x(2x - 7) - 2x(x + 1) = 7 \), b) \( 7x^2 - 28 = 0 \), c) \( 3x(x + 8) - x^2 - 2x(x + 1) = 2 \), d) \( (2x + 1) + x(2x + 1) = 0 \)

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Bài 6. Tìm x
a) \( x(2x - 7) - 2x(x + 1) = 7 \)
b) \( 7x^2 - 28 = 0 \)
c) \( 3x(x + 8) - x^2 - 2x(x + 1) = 2 \)
d) \( (2x + 1) + x(2x + 1) = 0 \)
e) \( 3x(x - 7) - 2(x - 7) = 0 \)
f) \( 2x^3 - 50x = 0 \)