If the function f(x) is defined for al real numbers x as the maximum value of 2x + 4 and 12 + 3x, then for which one of the following values of x will f(x) actually equal 2x + 4 ? [DCRU]
A. -5
B. -4
C. -9
D. -6

• Take values from options
  1) 2(-5)+4 = -6 , 12 + 3(-5) = -3
  2) 2(-4)+4 = -4 , 12 + 3(-4) = 0
  3) 2(-9)+4 = -14, 12 + 3(-9)= -15
  4) 2(-6)+4 = -8, 12 + 3(-6) = -6
  
  so that x = -4 gives the maximum value of 2x+4 and 12+3x
• 10 years agoHelpfull: Yes(19) No(6)
• since
  d(y)/d(x)=2x+4
  then
  d(y)=(2x+4)d(x)
  y=2*x*x/2+4*x
  y=x*x+4x
  put
  x=-4
  y=0
  then
  max value at x=-4
• 10 years agoHelpfull: Yes(7) No(1)
• for -9, 2x+4 is greater than 12+3x
• 10 years agoHelpfull: Yes(4) No(1)
• its -4 2x+4=2*(-4)+4 holds the maximum value here
• 10 years agoHelpfull: Yes(1) No(2)
• f(x)=max[2*x+4,12+3*x]
  for x=-9
  f(x)=max[-14,-15]=-14;
  so f(x) equals to 2*x+4
• 10 years agoHelpfull: Yes(1) No(0)