To find a set of 3 leg lengths that will form a right-angled triangle, the square of the largest leg must be equal to the sum of the squares of the other 2 legs.
We try out all the options:
39² = 1521, 15² + 36² = 1521.
12² = 144, 8² + 4² = 80.
17² = 289, 13² + 9² = 250.
Since 39² equals 15² + 36², option A is the correct answer.
When you solve, a quadratic formula is set up as ax^2+bx+c so in this scenario a is 1, b is -1 and c is -6. -(-1)+- √- 1^2-4(1)(-1)/2(1) is 1+/-√1+4/2 equals -2 and 3 making the answer c
