Question

Let x and y be two positive numbers whose sum is 175 and (x+3)(y+4) is a maximum

Answer 1

Explanation:

x+y = 175

y = 175 - x

f(x) = (x+3)(y+4)

= x(175-x) + 3(175-x) + 4x + 12

= 175x - x² + 525 - 3x + 4x + 12

= -x² +176x + 537

f'(x) = -2x + 176

maximum when x = 88

y = 175-x = 87