Answer:
9.8 cm
Explanation:
x = natural length
k*[(12 - x)² - (10 - x)²]/2 = 6 (1)
k*[(14 - x)² - (12 - x)²]/2 = 6 + 10 (2)
(1): k(144 + x² - 24x - 100 - x² + 20x) = 12
k(44 - 4x) = 12,
divide by 4, k(11 - x) = 3, k = 3/(11 - x)
(2): k(196 + x² - 28x - 144 - x² + 24x) = 32
k(52 - 4x) = 32
divide by 4, k(13 - x) = 8
3/(11 - x) * (13 - x) = 8
3(13 - x) = 8(11 - x)
39 - 3x = 88 - 8x
5x = 49
x = 9.8 cm