Step-by-step explanation:
the area is
(x² + 17x + 72) m²
it is the result of the usual
length × width
calculation.
length = x + g
width = x + h
length × width = x² + gx + hx + ab = x² + (g+h)x + gh =
= x² + 17x + 72
g + h = 17
gh = 72
just by looking at it that gives us 9 and 8 as g and h.
FYI - formally to calculate them we can say
g = 17 - h
(17 - h)h = 72
17h - h² = 72
h² - 17h + 72 = 0
the solution to such a quadratic equation is
x = (-b ± sqrt(b² - 4ac))/(2a)
in our case
x = h
a = 1
b = -17
c = 72
h = (17 ± sqrt(17² - 4×1×72))/(2×1) =
= (17 ± sqrt(289 - 288))/2 = (17 ± 1)/2
h1 = (17 + 1)/2 = 18/2 = 9
h2 = (17 - 1)/2 = 16/2 = 8
as we can see
g = 17 - h
if we say h = 9, then g = 8.
if we say h = 8, then g = 9.
so, these are our solutions.
we simply pick that length is longer than width, so, g = 9, h = 8.
the area including the walkway is then
(length + 3)(width + 3) =
= (x + 9 + 3)(x + 8 + 3) = (x + 12)(x + 11) m²
and the dimensions incl. the walkway are
length = x + 9 + 3 = x + 12
width = x + 8 + 3 = x + 11
