a) x+30%x=−1,3x+30%x=-1,3
⇔1310x=−1,3⇔1310x=-1,3
⇔x=−1⇔x=-1
Vậy x=−1x=-1
b) (2x+34)(x2−19)=0(2x+34)(x2-19)=0
⇔⇔ ⎡⎢ ⎢⎣2x+34=0x2−19=0[2x+34=0x2−19=0
⇔⇔ ⎡⎢ ⎢⎣x=−38x=29[x=−38x=29
Vậy S=−38;29S=−38;29
c) 7∣∣∣35x−40%∣∣∣−35:12=0,27|35x-40%|-35:12=0,2
⇔7∣∣∣35x−40%∣∣∣−65=0,2⇔7|35x-40%|-65=0,2
⇔7∣∣∣35x−40%∣∣∣=75⇔7|35x-40%|=75
⇔∣∣∣35x−40%∣∣∣=15⇔|35x-40%|=15
⇔⇔⎡⎢ ⎢⎣35x−25=1535x−25=−15[35x−25=1535x−25=−15
⇔⇔ ⎡⎣x=1x=13[x=1x=13
Vậy S={1;13}S={1;13}
d) x−58=2x−5x-58=2x-5
⇔(x−5)2=16⇔(x-5)2=16
⇔x2−5x−5x+25=16⇔x2-5x-5x+25=16
⇔x2−10x+9=0⇔x2-10x+9=0
⇔x2−x−9x+9=0⇔x2-x-9x+9=0
⇔x(x−1)−9(x−1)=0⇔x(x-1)-9(x-1)=0
⇔(x−9)(x−1)=0⇔(x-9)(x-1)=0
⇔⇔ [x−9=0x−1=0[x−9=0x−1=0
⇔⇔ [x=9x=1[x=9x=1
Vậy S={9;1}
