It is given in the question that
Anna buys 12 pens and 20 pencils for a total cost of $16. One pen costs $0.40 more than a pencil.
Let the cost of pencil is $ x .
Therefore cost of pen is
According to the question
Distributing 12 and combining like terms, we will get
Therefore cost of pencil is $0.35 and cost of pen is
Answer: (a) e ^ -3x (b)e^-3x
Step-by-step explanation:
I suggest the equation is:
d/dx[integral (e^-3t) dt
First we integrate e^-3tdt
Integral(e ^ -3t dt) as shown in attachment and then we differentiate the result as shown in the attachment.
(b) to differentiate the integral let x = t, and substitute into the expression.
Therefore dx = dt
Hence, d/dx[integral (e ^-3x dx)] = e^-3x
