(5a^3-4b)^2+(4b+5a^3)^2 = УПРОСТИТЬ

Решите задачу:

$(5a^3-4b)(5a^3-4b)+(4b+5a^3)^2$
$5a^3(5a^3)+5a^3(-4b)-4b(5a^3)-4b(-4b)+(4b+5a^3)^2$
$25a^6-40a^3b+16b^2+(4b+5a^3)^2$
$25a^6-40a^3b+16b^2+(4b+5a^3)(4b+5a^3)$
$25a^6-40a^3b+16b^2+(4b(4b)+4b(5a^3)+5a^3(4b)+5a^3(5a^3))$
$25a^6-40a^3b+16b^2+(16b^2+40a^3b+25a^6)$
$25a^6-40a^3b+16b^2+16b^2+40a^3b+25a^6$
$50a^6-40a^3b+16b^2+16b^2+40a^3b$
$50a^6+16b^2+16b^2+0$
$50a^6+16b^2+16b^2$
$50a^6+32b^2$