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(6)(a) y = k/x^2 2 = k/1^2 k = 2 y = 2/x^2 (b) y = 2/x^2 when x increase 30% % change of y = (New y - original y) x 100%/ original y = (2/(1.3x)^2 - 2/x^2)(100%) / (2/x^2) % change of y = -0.408 x 100% = -40.8% (y decreases 40.8%) (7) (a) z = kx/y (b) x increases 20%, y decreases 10% % change in z =(new z - original z) (100%) / original Z = (k(1.2x)/(0.9y) - kx/y)(100%)/(kx/y) = 33.3% (z increases 33.3%) (8)(a) T = km^2/n^2 where k is variation constant 8/5 = k(2^2)/(1^2) k = 2/5 T = 2m^2/5n^2 (b) T = 2(5^2)/5(4^2) T = 5/8 (c) m increases 15% and n increases 20% % change in T = (new T - original T)(100%) / original T = (2(1.15m)^2/5(1.2n)^2 - 2m^2/5n^2) (100%)/(2m^2/5n^2) = (0.918 - 1)(100%)/1 = -8.2% (T decreases 8.2%) (9) where k1 and k2 are variation constant t = k1√x -----(1) x = k2/y^2 ------(2) sub Eq(2) into Eq(1): t = k1√(k2/y^2) = C √(1/y^2) = C/y ( where C = k1/√k2) 3/√5 = C/1 C = 3/√5 t = 3/(y√5) (b) y = 3 t = 3/(3√5) t = 1/√5 (10) where a and k area variation constant C = kx + a/y^2 10 = 2k + a/(1^2) => 10 = 2k + a ----(1) 4 = k + a/(2^2) => 4 = k + a/4 ---(2) Eq(1) - 2Eq(2) = 2 = a - a/2 a = 4 sub into Eq(1): 10 = 2k + 4 k = 3 C = 3x + 4/y^2 (b) C = 3(3) + 4/4^2 = 9.25 = 37/4

其他解答:34CDDE34D73CDF8A