The answer is x^3+15x^2+75x+125
Work: (x+5)^3 , x^3+3x^2*5+3x*5^2+5^3 , 3x*25+125+x^3+15x^2 and you get x^3+15x^2+75x+125
2^30=1073741824
scientific notation is (number that is greater than or equal to 1 but less than 10) times 10^n
so
1073741824=
107374182.4 times 10¹=
10737418.24 times 10²=
etc
1.073741824 times 10⁹ is scientific nottaion
She can buy 「16,38/1,95」= 8 lunches
