stabiliti daca (7^4+7^5)x49 este cub perfect

Răspuns :

7^4(1+7^1)×7^2=
=7^4×8×7^2=
=7^6×2^3=
=(7^2×2)^3 = cub perfect
(7^4+7^5)×7^2=
=7^4×(1+7^1)×7^2=
=7^4×8×7^2=
=7^6×2^3=
=(7^2×2)^3=> cub perfect