Answer: [tex]k^4+10k^3+21k^2[/tex]
Step-by-step explanation:
Given
Height of rectangle is [tex]h=k^2+3k[/tex]
Width is [tex]w=k^2+7k[/tex]
The area of the rectangle is given by the multiplication of the height and width
[tex]\Rightarrow A=\left(k^2+3k\right)\left(k^2+7k\right)\\\\\Rightarrow A=k^2k^2+k^2\cdot \:7k+3kk^2+3k\cdot \:7k\\\\\Rightarrow A=k^4+10k^3+21k^2[/tex]
Thus, the area of the rectangle is [tex]k^4+10k^3+21k^2[/tex].
