Giải thích các bước giải:
a) (x - 3)² - x(x + 5) = 9
<=> x² - 6x + 9 - x² - 5x = 9
<=> (x² - x²) - (6x + 5x) = 0
<=> x = 0
b) (x+2)(x² - 2x + 4) - x(x² + 2) = 15
<=> x³ - 2x² + 4x + 2x² - 4x + 8 - x³ - 2x = 15
<=> -2x = 7
<=> x = -7/2
c) (x + 2)² - 9 =0
<=> (x + 2)² = 9
<=> x + 2 = -3, x + 2 = 3
<=> x = {-5; 1}
d) 6x² - (2x + 5)(3x - 2) = 7
<=> 6x² - 6x² + 4x - 15x + 10 = 7
<=> -11x = -3
<=> x = 3/11
e) (5 - 3x)² - 36 = 0
<=> (5 - 3x)² = 36
<=> 5 - 3x = -6, 5 - 3x = 6
<=> x = {11/3; -1/3}
f) (x + 3)² - (x - 5)² = 0
x² + 6x + 9 - x² + 10x - 25 = 0
<=> 16x = 16
<=> x = 1
g) (5 - x)(25 + 5x + x²) + x(x² - 7) = 25
<=> 125 + 25x + 5x² - 25x - 5x² - x³ + x³ - 7x = 25
<=> 125 - 7x = 25
<=> 7x = 100
<=> x = 100/7
h) (7 - 2x)² + (3 + 2x)(3 - 2x) = 30
<=> 49 - 28x + 4x² + 9 - 4x² = 30
<=> 58 - 28x = 30
<=> 28x = 28
<=> x = 1
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