giải pt a,2x(x-5)-x+5=0 b,(x+3)2-(5-x)(x+3)=0 c,(x+2)(3-4x)=x2+4x+4

2 câu trả lời

Đáp án:

a)

2x(x-5)-x+5=0

2x(x-5)-(x-5)=0

(x-5)(2x-1)=0

[x5=02x1=0

[x=52x=1

[x=5x=12

Vậy S={5;12}

b)

(x+3)2-(5-x)(x+3)=0

(x+3)(x+3-5+x)=0

(x+3)(2x-2)=0

(x+3).2.(x-1)=0

(x+3)(x-1)=0

[x+3=0x1=0

[x=3x=1

Vậy S={-3;1}

c)

(x+2)(3-4x)=x2+4x+4

(x+2)(3-4x)=x2+2.x.2+22

(x+2)(3-4x)-(x+2)2=0

(x+2)(3-4x-x-2)=0

(x+2)(-5x+1)=0

[x+2=05x+1=0

[x=25x=1

[x=2x=15

Vậy S={-2;15}

a)2x(x-5)-x+5=0

2x(x-5)-(x-5)=0

(2x-1)(x-5)=0

2x-1=0 hay x-5=0

x=12hay x=5

b)(x+3)2-(5-x)(x+3)=0

(x+3)(x+3-5+x)=0

x+3=0 hay 2x-2=0

x=-3 hay x=1

c)(x+2)(3-4x)=x2+4x+4

(x+2)(3-4x)-(x+2)2=0

(x+2)(3-4x-x-2)=0

x+2=0 hay -5x+1=0

x=-2 hay x=15

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