Bài 1.Bỏ dấu ngoặc rồi thu gọn biểu thức
a, A = ( a + b ) – ( a – b ) + ( a – c ) – ( a + c )
b, B = ( a + b – c ) + ( a – b + c ) – ( b + c – a ) – ( a – b – c )
Bài 2. Tìm x
a, 5 – ( 10 – x ) = 7
b, -32 – ( x – 5 ) = 0
c, -12 + ( x – 9 ) = 0
d, 11 + ( 15 – x ) = 1
Đáp án:
`↓↓↓`
Giải thích các bước giải:
Bài `1` :
`a ) A = ( a + b ) – ( a – b ) + ( a – c ) – ( a + c )`
`A = a + b – a + b + a – c – a – c`
` A = ( a – a + a – a ) + ( b + b ) + ( – c – c )`
` A = 0 + 2b – 2c = 2 ( b – c )`
`b ) B = ( a + b – c ) + ( a – b + c ) – ( b + c – a ) – ( a – b – c )`
` B = a + b – c + a – b + c – b – c + a – a + b + c`
` B = ( a + a + a – a ) + ( b – b – b + b ) + ( – c + c – c + c ) `
` B = 2a + 0 + 0 = 2a`
Bài `2` :
`a ) 5 – ( 10 – x ) = 7`
`10 – x = 5 – 7 = ( -2 )`
`x = 10 – ( -2 ) = 10 + 2`
`x = 12`
Vậy `x = 12`
`b ) -32 – ( x – 5 ) = 0`
` x – 5 = – 32`
`x = -32 + 5`
` x = – 27`
Vậy `x = -27`
`c ) -12 + ( x – 9 ) = 0`
` x – 9 = 0 – ( -12 ) = 12`
` x = 12 + 9 = 21`
Vậy `x = 21`
`d ) 11 + ( 15 – x ) = 1`
`15 – x = 1 – 11 `
` 15 – x = -10`
`x = 15 – ( -10 ) = 15 + 10`
`x = 25`
Vậy `x = 25`
Bài $1$ :
`a)A=(a+b)-(a-b)+(a-c)-(a+c)`
`A=a+b-a+b+a-c-a-c`
`A=(a-a+a-a)+(b+b)+(-c-c)`
`A=0+2b-2c=2b-2c`
`A=b-c`
`b)B=(a+b-c)+(a-b+c)-(b+c-a)-(a-b-c)`
`B=a+b-c+a-b+c-b-c+a-a+b+c`
`B=(a+a+a-a)+(b-b-b+b)+(-c+c-c+c)`
`B=(3a-a)+(0-b+b)+(-c+c)`
`A=2a+0+0`
`B=2a`
Bài $2$ :
`a)5-(10-x)=7`
`10-x=5-7`
`10-x=(-2)`
`x=10-(-2)`
`x=12`
`b)-32-(x-5)=0`
`x-5=-32-0`
`x-5=-32`
`x=-32+5`
`x=-27`
`c)-12+(x-9)=0`
`x-9=0-(-12)`
`x-9=12`
`x=12+9`
`x=21`
`d)11+(15-x)=1`
`15-x=1-11`
`15-x=(-10)`
`x=15-(-10)`
`x=15`