Đáp án: + Giải thích các bước giải:
Bài 1 :
`a//`
`(-8)/13 - ( 3/7 + 5/13 )`
`= (-8)/13 - 74/91`
`= (-56)/91 - 74/91`
`= (-130)/91`
`b//`
`(-5)/7 . 2/11 + (-5)/7 . 9/11 + 1 5/7`
`= (-5)/7 . ( 2/11 + 9/11 ) + 12/7`
`= ( 12/7 + (-5)/7 ) . ( 2/11 + 9/11 )`
`= 7/7 . 11/11`
`= 1 . 1`
`= 1`
`c//`
`( 4 - 5/12 ) : 2 + 5/24`
`= ( 48/12 - 5/12 ) : 2 + 5/24`
`= 43/12 : 2 + 5/24`
`= 43/24 + 5/24`
`= 48/24 = 2`
Bài 2 :
`a//`
`| x - 1/3 | : 2 = (-2)^2 + 4/6`
`⇒ | x - 1/3 | : 2 =(-4) + 4/6`
`⇒ | x - 1/3 | = (-20)/6 : 2`
`⇒ | x - 1/3 | = (-20)/12`
`⇔ x - 1/3 = ± (-20)/12`
Trường hợp 1 :
`x - 1/3 = (-20)/12`
`⇒ x = (-20)/12 + 1/3`
`⇒ x = (-16)/12 = (-4)/3`
Trường hợp 2 :
`x - 1/3 = -(-20)/12`
`⇒ x - 1/3 = 20/12`
`⇒ x = 20/12 + 1/3`
`⇒ x = 24/12 = 2`
Vậy `x ∈ { 2 ; (-4)/3 }`
`b//`
`(x + 1/10)^2 + 5/16 = 14/3 . 3/16`
`⇒ ( x + 1/10)^2 + 5/16 = 42/48`
`⇒ ( x + 1/10 + 5/16 )^2 = 7/8`
`⇒ ( x + 66/160)^2 = 7/8`
`⇒ (x + 33/80)^2 = 70/80`
`⇒ x + 33/80 = ± (\sqrt{70})/80`
`⇒ x = (33±\sqrt{70})/80`
Vậy `x ∈ { (33±\sqrt{70})/80 }`
