This is normal, and the arbitrary function all can approach with dividing section multinomials because can know from infinitesimalcalculus.
这是正常的,因为从微积分可以知道,任一函数都可以用分段多项式来逼近。
3
For if these increases of income or utility are reduced to being infinitesimal, one can use both the symbolism and the powerful manipulations of the differential calculus.