Đáp án:
Bài `3`
`a)`
` x + (-13) = -114`
` => x -13 =114`
` x = 114 + 13`
` x = 127`
b)
` 453 + x = -443 - (-199)`
` 453 + x = -443 + 199`
` 453 + x = -244`
` x = 453 + 244`
` x = 697`
c)
` 5x - (-15) = (-16) - 14`
` 5x + 15 = - (16 +14)`
` 5x + 15 = -30`
` 5x = -45`
` x =-9`
d)
` 2|x-5| -23 = -5`
` 2|x-5| = 18`
` |x-5| = 9`
TH1
` x -5 = 9`
` x = 14`
TH2
` x -5 = -9`
` x = -4`
e)
` (2x-1)^2 = 81`
TH1
` 2x -1 = 9`
` 2x = 10`
` x= 5`
TH2
` 2x -1 = -9`
` 2x = -8`
`x = -4`
`f)`
` (4-2x)(x-3) = 0`
TH1
` 4 -2x = 0`
` 2x = 4`
` x = 2`
TH2
` x-3 = 0`
` x =3`
Bài 4
a)
` x ∈ { -4; -3;-2; -1;1;2;3 }`
` => -4 + (-3) + (-2) + (-1) +1 + 2 +3 = -4`
b)
` x ∈ { -15; -14; -13; -12; .. ; 18;19}`
` => (-15+ 15) + (-14+14) +..... + 16 + 17 +18+19 = 70`
Bài 5
a)
` | 3x-6| \geq 0`
` => |3x-6| + 5 \geq 5`
` => A_{min}= 5` khi ` x= 2`
b)
` B = |2-x| -3 \geq 0 -3= -3`
` => B_{min} = -3` khi ` x= 2`