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
⇔[x−5=02x−1=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=0x−1=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=0−5x+1=0
⇔[x=−2−5x=−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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