Explanation:
4⁵ × 4^-7 / 4^-2
it is important to understand that a negative exponent means 1/...
a^-n = 1/(a^n)
in that sense we have therefore
4⁵ × 1/4⁷ × 4² (as (1/ 1/a^n) = a^n)
4⁵ × 4² × 1/4⁷ = 4⁷ × 1/4⁷ = 1
so, "1" is the fully simplified expression equal to the original expression.