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1. Factorize 25h^2-(h^2+8h+16) .點計到個answer係 8(3+2)(-1) .2.Volum of the cubid : 2(x+1)^3-12(x+1)^2+18(x+1) , the base of a cubiod is a square with sides of (x-2)cm each , the height of the cubiod : 2(x+1)cm(a) If the side of a square is equal to the height of the cubiod,the area of the square is... 顯示更多 1. Factorize 25h^2-(h^2+8h+16) .點計到個answer係 8(3+2)(-1) . 2.Volum of the cubid : 2(x+1)^3-12(x+1)^2+18(x+1) , the base of a cubiod is a square with sides of (x-2)cm each , the height of the cubiod : 2(x+1)cm (a) If the side of a square is equal to the height of the cubiod,the area of the square is (Ax^2+Bx+c)cm^2.Find the values of A,B and C. 更新: 3. Pentagon ABCDE is formed by rectangle BCDE and right-angled isoscles triangle ABE.If BC:CD=3:5 and the perimeter of BCDE is 19.2 cm,find the are of the pentagon.

最佳解答:

1. 25h^2-(h^2+8h+16) = (5h)^2 - (h + 4)^2 = (5h + h + 4)(5h - h - 4) = (6h + 4)(4h - 4) = [2(3h + 1)][4(h - 1)] = 8(3h + 1)(h - 1) 2. "If the side of a square is equal to the height of the cubiod" , then x - 2 = 2(x + 1) x計出來係負數.......係咪抄錯? 3. Let BC = 3k and CD = 5k 2(3k + 5k) = 19.2 k = 1.2 therefore, BC = 3.6 and CD = 6 As triangle ABE is isoscles, therefore AB = AE By Pyth.Theorem, 2AB^2 = BE^2 2AB^2 = 36 AB^2 = 18 AB = 3開方2 Area is the pentagon = 1/2(AB)^2 + CD * BC = 1/2(3開方2)^2 + 3.6 * 6 = 9 + 21.6 = 30.6 cm^2

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