Máy lạnh tiêu tốn công 600kJ và thải nhiệt cho nguồn nóng 2000kJ. Hãy tính hệ số làm lạnh của chu trình?

Stealthily, eerily, nervously, fearfully, excitedly, sheepishly, immediately

Ithink its answer a)

You need to figure out at which x-value does the graph has a tangent line slope of -1.remember, the derivative is the slope of the tangent line. so find the derivative function and set it to equal -1 to find the x-value that will have a tangent line slope of 0.differentiate with the chain rule.    set the derivative to equal -1 and solve for x.      take log base 10 of both sides. also recall that  .    so the x-coord of the point of tangency is .the y-coordinate of this point of tangency can be calculated using the original function:     using point-slope form, the equation of the tangent line is      the x-intercept of this tangent line is when the graph is at y=0.    this rounds off to  .choice c.