Đáp án
1, (x - 3)(2x - 1) = (2x-1)(2x+3)
<=> (x-3)(2x-1)-(2x-1)(2x+3) = 0
<=> (2x-1)(x-3-2x-3) = 0
<=> (2x - 1)(-x +6) = 0
=> 2x -1 =0 => x= 1/2
=> -x + 6 = 0 => x = 6
2, (5+4x)(-x+2)=(5+4x)(7+5x)
<=> (5+4x)(-x+2)-(5+4x)(7+5x) = 0
<=> (5+4x)(-x+2-7-5x)= 0
<=> (5+4x)(-6x-5) = 0
=> 5+4x = 0 => x = -5/4
=> -6x-5=0 => x = -5/6
3, (4+x)(x-5)=(3x-8)(x-5)=0
*<=> (4+x)(x-5)=0
=> 4+x =0 => x= -4
=> x-5 = 0 => x = 5
* <=> (3x-8)(x-5)=0
=> 3x-8 = 0 => x = 8/3
=> x-5 = 0 => x = 5
4, (3x-8)(7-21x)=(9+2x)(7-21x)
<=> (3x-8)(7-21x)-(9+2x)(7-21x) = 0
<=> (7-21x)(3x-8-9-2x) = 0
<=> (7-21x)(x-17) = 0
=> 7-21x = 0 => x = -7/21
=> x-17 = 0 => x = 17
* Chúc bạn học tốt nha :)))))
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