Answer:
Dimensions of printed poster are
length is 32 cm
width is 48 cm
Step-by-step explanation:
Let's assume
length of printed poster is x cm
width of printed poster is y cm
now, we can find area of printed poster
so, area of printed poster is
![=xy](https://tex.z-dn.net/?f=%3Dxy)
we are given that area as 1536
so, we can set it to 1536
![xy=1536](https://tex.z-dn.net/?f=xy%3D1536)
now, we can solve for y
![y=\frac{1536}{x}](https://tex.z-dn.net/?f=y%3D%5Cfrac%7B1536%7D%7Bx%7D)
now, we are given
The top and bottom margins of a poster are each 12 cm and the side margins are each 8 cm
so, total area of poster is
![A=(8+x+8)\times (12+y+12)](https://tex.z-dn.net/?f=A%3D%288%2Bx%2B8%29%5Ctimes%20%2812%2By%2B12%29)
![A=(x+16)\times (y+24)](https://tex.z-dn.net/?f=A%3D%28x%2B16%29%5Ctimes%20%28y%2B24%29)
now, we can plug back y
![A=(x+16)\times (\frac{1536}{x}+24)](https://tex.z-dn.net/?f=A%3D%28x%2B16%29%5Ctimes%20%28%5Cfrac%7B1536%7D%7Bx%7D%2B24%29)
now, we have to minimize A
so, we will find derivative
![A'=\frac{d}{dx}\left(\left(x+16\right)\left(\frac{1536}{x}+24\right)\right)](https://tex.z-dn.net/?f=A%27%3D%5Cfrac%7Bd%7D%7Bdx%7D%5Cleft%28%5Cleft%28x%2B16%5Cright%29%5Cleft%28%5Cfrac%7B1536%7D%7Bx%7D%2B24%5Cright%29%5Cright%29)
we can use product rule
![A'=\frac{d}{dx}\left(x+16\right)\left(\frac{1536}{x}+24\right)+\frac{d}{dx}\left(\frac{1536}{x}+24\right)\left(x+16\right)](https://tex.z-dn.net/?f=A%27%3D%5Cfrac%7Bd%7D%7Bdx%7D%5Cleft%28x%2B16%5Cright%29%5Cleft%28%5Cfrac%7B1536%7D%7Bx%7D%2B24%5Cright%29%2B%5Cfrac%7Bd%7D%7Bdx%7D%5Cleft%28%5Cfrac%7B1536%7D%7Bx%7D%2B24%5Cright%29%5Cleft%28x%2B16%5Cright%29)
![=\frac{d}{dx}\left(x+16\right)\left(\frac{1536}{x}+24\right)+\frac{d}{dx}\left(\frac{1536}{x}+24\right)\left(x+16\right)](https://tex.z-dn.net/?f=%3D%5Cfrac%7Bd%7D%7Bdx%7D%5Cleft%28x%2B16%5Cright%29%5Cleft%28%5Cfrac%7B1536%7D%7Bx%7D%2B24%5Cright%29%2B%5Cfrac%7Bd%7D%7Bdx%7D%5Cleft%28%5Cfrac%7B1536%7D%7Bx%7D%2B24%5Cright%29%5Cleft%28x%2B16%5Cright%29)
now, we can simplify it
![A'=-\frac{24576}{x^2}+24](https://tex.z-dn.net/?f=A%27%3D-%5Cfrac%7B24576%7D%7Bx%5E2%7D%2B24)
now, we can set it to 0
and then we can solve for x
![A'=-\frac{24576}{x^2}+24=0](https://tex.z-dn.net/?f=A%27%3D-%5Cfrac%7B24576%7D%7Bx%5E2%7D%2B24%3D0)
![-\frac{24576}{x^2}x^2+24x^2=0\cdot \:x^2](https://tex.z-dn.net/?f=-%5Cfrac%7B24576%7D%7Bx%5E2%7Dx%5E2%2B24x%5E2%3D0%5Ccdot%20%5C%3Ax%5E2)
![-24576+24x^2=0](https://tex.z-dn.net/?f=-24576%2B24x%5E2%3D0)
![x=32,\:x=-32](https://tex.z-dn.net/?f=x%3D32%2C%5C%3Ax%3D-32)
Since, x is dimension
and dimension can never be negative
so, we will only consider positive value
![x=32](https://tex.z-dn.net/?f=x%3D32)
now, we can solve for y
![y=\frac{1536}{32}](https://tex.z-dn.net/?f=y%3D%5Cfrac%7B1536%7D%7B32%7D)
![y=48](https://tex.z-dn.net/?f=y%3D48)
so, dimensions of printed poster are
length is 32 cm
width is 48 cm