Đáp án:
Giải thích các bước giải:
bài 5
1) x-5=0
⇔x=5
vậy x=5
2) 2x+4=0
⇔2x=-4
⇔x=$\frac{-4}{2}$
⇔x=-2
vậy x=-2
3)3x-2=0
⇔3x=2
⇔x=$\frac{2}{3}$
vậy x=$\frac{2}{3}$
4)2(x-1)=5
⇔x-1=$\frac{5}{2}$
⇔x=$\frac{5}{2}$ + 1
⇔x=$\frac{5}{2}$ +$\frac{2}{2}$
⇔x= $\frac{7}{2}$
vậy x=$\frac{7}{2}$
5) 3x(12x-4)-9x(4x-3)=30
⇔36x²-12x-36x²+27x=30
⇔15x=30
⇔x=$\frac{30}{15}$
⇔x=2
vậy x=2
6) x(5-2x)+2x(x-1)=15
⇔5x-2x²+2x²-2x=15
⇔3x=15
⇔x=15:3
⇔x=5
vậy x=5
7) 2x(x-5)-x(3+2x)=26
⇔2x²-10x-3x-2x²=26
⇔-13x=26
⇔x=26:(-13)
⇔x=-2
vậy x=-2
8)3x+2(5-x)=0
⇔3x+10-2x=0
⇔x+10=0
x=-10
vậy x=-10
9)3x²-3x(-2+x)=36
⇔3x²+6x-3x²=36
⇔ 6x=36
⇔x=36:6
⇔x=6
vậy x=6
10) $\frac{1}{3}$ x - 4x +2x(2-3x)=0
⇔$\frac{1}{3}$ x-4x+4x-6x²=0
⇔$\frac{1}{3}$x-6x²=0
⇔x($\frac{1}{3}$-6x)=0
⇔$\left \{ {{x=0} \atop {$\frac{1}{3}$-6x=0}} \right.$
⇔$\left \{ {{x=0} \atop {6x=$\frac{1}{3}$}} \right.$
⇔$\left \{ {{x=0} \atop {x=$\frac{1}{3}$:6}} \right.$
⇔$\left \{ {{x=0} \atop {x=$\frac{1}{3}$.$\frac{1}{6}$ }} \right.$
⇔$\left \{ {{x=0} \atop {x=$\frac{1}{18}$ }} \right.$
vậy $\left \{ {{x=0} \atop {x=$\frac{1}{18}$ }} \right.$
11) 5(2x-1)-4(8-3x)=-5
⇔10x-5-32+12x=-5
⇔22x-37=-5
⇔22x=-5+37
⇔22x=32
⇔x=$\frac{32}{22}$
⇔x=$\frac{16}{11}$
vậy x=$\frac{16}{11}$
12)4x(x-1)-4(x²-5)=(x-3)-(x+4)
⇔4x²-4x-4x²+20=x-3-x-4
⇔4x²-4x-4x²-x+x=-3-4-20
⇔-4x=-27
⇔x=$\frac{27}{4}$
vậy x=x=$\frac{27}{4}$
13) 7(2x-5)-5(7x-2)+2(5x-7)=-6
⇔14x-35-35x+10+10x-14=-6
⇔14x-35x+10x=-6+14-10+35
⇔-11x=33
⇔x=33:(-11)
⇔x=-3
vậy x=-3
14)5x(12x+7)-3x(20x-5)=-100
⇔ 60x²+35x-60x²+15x=-100
⇔50x=-100
⇔x=-100/50
⇔x=-2
vậy x=-2
15)4x(x-1)-3(x²-5)-x²=(x-3)-(x-4)
⇔ 4x²-4x-3x²+15-x²=x-3-x+4
⇔4x²-4x-3x²-x²-x+x=-3+4-15
⇔-4x=-14
⇔x=14/4
vậy x=14/4
