1 . Tìm x ∈ N
1. (x – 15 ) – 75
2. ( 315 + (125 -x ) = 435
3. x – 105 : 21 = 15
4. [ (x + 32 ) – 17 ] . 2 = 42
1 . Tìm x ∈ N 1. (x – 15 ) – 75 2. ( 315 + (125 -x ) = 435 3. x – 105 : 21 = 15 4. [ (x + 32 ) – 17 ] . 2 = 42
By Autumn
By Autumn
1 . Tìm x ∈ N
1. (x – 15 ) – 75
2. ( 315 + (125 -x ) = 435
3. x – 105 : 21 = 15
4. [ (x + 32 ) – 17 ] . 2 = 42
1. (x – 15 ) = 75
x = 75 + 15
x = 90
2. ( 315 + (125 – x ) = 435
315 + 125 – x = 435
340 – x = 435
x = 435 – 340
x = 90
3. x – 105 : 21 = 15
x – 105 = 15 . 21
x – 105 = 315
x = 315 + 105
x = 420
4. [ (x + 32 ) – 17 ] . 2 = 42
( x + 32 ) – 17 = 42 : 2
( x + 32 ) – 17 = 21
x + 32 = 21 + 17
x + 32 = 38
x = 38 – 32
x = 4
1. (x – 15 ) = 75
⇒ x – 15 = 75
⇒ x = 75 + 15
⇒ x = 90
2. ( 315 + (125 – x ) = 435
⇒ 315 + 125 – x = 435
⇒ 340 – x = 435
⇒ x = 435 – 340
⇒ x = 90
3. x – 105 : 21 = 15
⇒ x – 105 = 15 . 21
⇒ x – 105 = 315
⇒ x = 315 + 105
⇒ x = 420
4. [ (x + 32 ) – 17 ] . 2 = 42
⇒ ( x + 32 ) – 17 = 42 : 2
⇒ ( x + 32 ) – 17 = 21
⇒ x + 32 = 21 + 17
⇒ x + 32 = 38
⇒ x = 38 – 32
⇒ x = 4