Solution 4.1 on Applications of Relations and Functions
- x2 – 6 + 9 factors into (x – 3)(x – 3). Since this represents the area of a square,
Where length = width, then (x – 3) = length and ( x – 3) = width.
Perimeter of a square = 2(length + width) = 2((x – 3) + (x – 3)) = 2(2x – 6)
= 2(18 – 6) = 2 ´ 12 = 24.
Answer B
2. Let the numbers be x and y. We are given x + y = 13
- y = 13 –x and xy = 42.
By substituting this y in xy = 42, we get x(13-x) = 42. This is quadratic equation x2 – 13x + 42 = 0 whose solution gives the numbers to be 6 and 7.
Answer A