4x + 5y = 4(2) + 5(1) = 8 + 5 = 13
For this case we must raise an inequality.
We have "d" dollars initially and they are spent 12. Then:

At least 51 dollars remain, then, the sign of inequality is greater or equal in favor of the expression
, that is:

Resolving:

There are at least 63 dollars left in the account.
Answer:

By the fundamental theorem of calculus,

So we have



F(x) = 4x + 7
g(x) = 3x²
(f · g)(x) = 3x²(4x + 7)
(f · g)(x) = 3x²(4x) + 3x²(7)
(f · g)(x) = 12x³ + 21x²