The formula of an area of a rectangle:
[tex]A=lw[/tex]
l - length
w - width
We have w = l - 4 and A = 45 in²
Therefore we have the equation:
[tex]l(l-4)=45[/tex] use distributive property
[tex]l^2-4l=45[/tex] subtract 45 from both sides
[tex]l^2-4l-45=0\\\\l^2+5l-9l-45=0\\\\l(l+5)-9(l+5)=0\\\\(l+5)(l-9)=0\iff l+5=0\ \vee\ l-9=0\\\\l=-5 < 0\ \vee\ \boxed{l=9}[/tex]
Answer: C. 9 inches
