Concept: Let small charge in x be ?x and the corresponding change in y is ?y.\(\rm ? y = \rm \dfrac{dy}{dx}? x = f'(x) ? x \)Now that ?y = f(x + ?x) - f(x)Therefore, f(x + ?x) = f(x) + ?yCalculation: Given: f(x) = 2x3 + 5xf'(x) = 6x2 + 5Let x + ?x = 2.05 = 2 + 0.05Therefore, x = 2 and ?x = 0.05f(x + ?x) = f(x) + ?y= f(x + ?x) = f(x) + f'(x)?x= f(2.05) = 2x3 + 5x + (6x2 + 5)?x= f(2.05) = 2(2)3 + 5(2) + [6?(2)2 + 5](0.05)= f(2.05) = 16 + 10 + (24 + 5)(0.05)= f(2.05) = 26 + (29)(0.05)= f(2.05) = 26 + 1.45 = 27.45