Question

write a quadratic function f(x) for the area of a rectangle length x+5 width 3x-7

Answer 1

The area of a rectangle is the product of its length and width.
$l=x+5 \\ w=3x-7 \\ \\ A=lw=(x+5)(3x-7)=3x^2-7x+15x-35=3x^2+8x-35 \\ \\ \boxed{f(x)=3x^2+8x-35}$