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標題:

F2 math (20points)

發問:

圖片參考：http://img341.imageshack.us/img341/4513/94985761.png thx~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

最佳解答:

1. 45(9x/5 - y)(5y/9 + x) = 5(9x/5 - y)·9(5y/9 + x) = (9x - 5y)(5y + 9x) = (9x + 5y)(9x - 5y) = (9x)2 - (5y)2 = 81x2 - 25y2 2. 3a(4b - 1) + 2a(1 - 4b) = 3a(4b - 1) - 2a(4b - 1) = (3a - 2a)(4b - 1) = a(4b - 1) 3. (5x - 2)(y - 3z) - (2 - 5x)(3y - z) = (5x - 2)(y - 3z) + (5x - 2)(3y - z) = (5x - 2)[(y - 3z) + (3y - z)] = (5x - 2)(y - 3z + 3y - z) = (5x - 2)(4y - 4z) = 4(5x - 2)(y - z) 4. (4x + 2x2)/(2 + x)2 = 2x(2 + x)/(2 + x)2 = 2x/(2 + x) 5. (2a - 2b)/3a ÷ (b - a)/9ab = 2(a - b)/3a x 9ab/[-(a - b)] = -6b 6. a. C = 2πr r = C/2π b. A = 2πr2 + 2πrh A = 2π(C/2π)2 + 2π(C/2π)h A = (C2/2π) + Ch c. A = (C2/2π) + Ch A = (222/2)x(7/22) + 22x3 A = 143

其他解答:6A560DB68EC65D60