a/
`A =x^3 +6x^2 +12x+8`
`<=> A = x^3 + 3 . x^2 . 2 + 3 . x . 2^2 + 2^3`
`<=> A = (x+2)^3`
`<=> A = (48+2)^3 =50^3 =125000`
Vậy `A = 125000 <=> x = 48` .
c/
Sửa đề xíu : `C = (y-x/2)^3 -6(y-x/2)^2 +12(y-x/2) -8` .
`C = (y-x/2)^3 -6(y-x/2)^2 +12(y-x/2) -8`
`<=> C = (y-x/2)^3 - 3 . (x/2 - y)^2 . 2 + 3 . ( y -x/2) . 2^2 -2^3`
`<=> C = (y-x/2 - 2)^3`
`<=> C = (1 - 206/2 -2)^3`
`<=> C = (-104)^3`
Vậy `C = (-104)^3 <=> x =206` và `y =1`
d/
`D = (7-x)(x^2+7x+49) -(64 -x^3)`
`<=> D = 7^3 -x^3 - 64 +x^3`
`<=> D =279`
Vậy `D =279<=> x =2017` .