tìm x : a ) (2x+5)(2x-7)-(-4x-3)^2=16 b) (8x^2+3)(8x^2-3)-(8x^2-1)^2=22 c) 2(x-1)^2-(2-x)^2-(x-3)(x+3)=0
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1 câu trả lời 3765
a)(2x+5)(2x−7)−(−4x−3)2=16⇔4x2−14x+10x−35−(16x2+24x+9)=16⇔4x2−4x−35−16x2−24x−9=16⇔−12x2−28x−44=16⇔12x2+28x+60=0⇔3x2+7x+20=0⇔3(x2+73x+4936)+19112=0⇔3(x+76)2+19112=0do:3(x+76)2≥0=>3(x+76)2+19112≥19112>0
vậy pt vô nghiệm
b)(8x2+3)(8x2−3)−(8x2−1)2=22⇔(8x2)2−32−(64x4−16x2+1)=22⇔64x4−9−64x4+16x2−1=22⇔16x2−10=22⇔16x2=32⇔x2=2⇔x=±√2vay:S={√2;−√2}c)2(x−1)2−(2−x)2−(x−3)(x+3)=0⇔2(x2−2x+1)−(4−4x+x2)−(x2−9)=0⇔2x2−4x+2−4+4x−x2−x2+9=0⇔7=0
=>VÔ lý
vbayaj pt vô nghiệm
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