This is an anti-derivative problem. You need to choose two different letters for your constant of variation (+C and +D perhaps) and then use the two points to solve for C and D.
f '(x) = 4x+3x^2+12x^3+C
f(x) = 2x^2+x^3+3x^4+Cx+D
f(0)=5 --> D = 5
f(1)=15 --> 15=2+1+3+C+5 --> C = 4
f(x) = 2x^2+x^3+3x^4+5x+4
Mary A.
Thank you!05/04/21