$\\$
`1,`
`a,`
`(3x-1)(2x+7) - (12x^3 + 8x^2 - 14x):2x`
`= 6x^2 + 21x - 2x-7 - (6x^2 + 4x - 7)`
`= 6x^2 + 19x - 7 - 6x^2 - 4x+7`
`= 15x`
`b,`
`B=(63^3 - 37^3) : 26 + 63. 37`
`= (63 - 37) (63^2 + 63 . 37 + 37^2) : 26 + 63 . 37`
`= (63^2 + 63 . 37 + 37^2) . 26 : 26 + 63 . 37`
`= 63^2 + 63 . 37 +37^2 + 63.37`
`= 63^2 + 2 . 63 . 37 + 37^2`
`= (63+37)^2`
`= 100^2`
`= 100 00`
Vậy `B=100 00`