Bài 1:
1, 2x+12=3x-21
<=>x=33
2, 2.x^2-1=49
<=>2x^2=50
<=>x^2=25
<=>x=5 hoặc x=-5
Bài 2:
1, x(x+3)=0
x=0 hoặc x+3=0
x=0 x=-3
2, (x-2)(5-x)=0
x-2=0 hoặc 5-x=0
x=2 x=5
3, (x-1)(x^2+1)=0
x-1=0 hoặc x^2+1=0
x=1 x^2=-1<vô lí>
Vậy x=1
4, -12(x-5)+7(3-x)=5
<=>-12x+50+21-7x-5=0
<=>-19x+66=0
<=>x=66/19
5, 30(x+2)-6(x-5)-24x=100
<=>30x+60-6x+30-24x-100=0
<=>0x-40=0
<=>0x=40
=> Phương trình vô nghiệm
=>>>>>>>>>>>>>>>>
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