Question

Answer 1

a) 12 - |3x - 5| = 2

|3x - 5| = 12 - 2

|3x - 5| = 10

3x - 5 = 10 và 3x - 5 = -10

*) 3x - 5 = 10

3x = 10 + 5

3x = 15

x = 15 : 3

x = 5

*) 3x - 5 = -10

3x = -10 + 5

3x = -5

x = -5/3

Vậy x = -5/3; x = 5

b) 5/x = x/80

x² = 5.80

x² = 40

x = 20 hoặc x = -20

Answer 2

a.12-|3x-5|=2

|3x-5|=12-2=10

⇒3x-5=10;3x-5=-10

+3x-5=10

3x=10+5=15

x=15:3=5

+3x-5=-10

3x=-10+5=-5

x=-5:3=5/3

b.5/x=x/80

⇒5.80=x²

⇒400=x²

⇒20²=x²

⇒x=20

Answer 3

`a) 12-|3x-5| =2`

`<=> |3x-5| = 12-2 =10`

`=> [(3x-5=10),(3x-5 =-10):}`

`<=> [(3x=10+5=15),(3x=-10+5=-5):}`

`<=>[(x=15/3 =5),(x=-5/3):}`

Vậy `x in {5;-5/3}`

`b) 5/x = x/80 `

`<=> x^2 = 400`

`=> [(x=20),(x=-20):}`

Vậy `x = +- 200`