113
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13
f(x) = x² - x + 5, x > 1/2y = x² - x + 5x² - x + 5 - y = 0x = 1 ± √(1 + 4(y - 5))/2g(x) = 1 ± √(1 + 4(x - 5))/2g'(x) = 4 × 1/(2√(1 + 4(x - 5))) × 1/2g'(x) = 1/√(1 + 4(x - 5))g'(7) = 1/√(1 + 4(7 - 5)) = 1/√9 = 1/3