Answer:
5
Step-by-step explanation:
area of rectangle = l(ength)×w(idth)
perimeter = 2×l + 2×w
diagonal = sqrt(l² + w²) (Pythagoras)
l×w = 12. => l = 12/w
2×l + 2×w = 14
2×12/w + 2×w =14
12/w + w = 7
12 + w² = 7w
w² - 7w + 12 = 0
=> (after a little thinking and trying : what 2 numbers multiply to 12 and add to -7 ? -3 and -4
=> (w-3)×(w-4) = 0
so, we get 2 solutions for w : 3 and 4
that gives us 2 solutions for l : 4 and 3
so, one is 3 and the other 4. it does not matter which is which. length 4 and width 3 produce the same diagonal as length 3 and width 4.
diagonal = sqrt(l² + w²) = sqrt(16 +9) = sqrt(25) = 5
