標題:

f.4 maths

發問:

http://i64.photobucket.com/albums/h182/mandy888877/222.jpg pls explain the ans why>< thanks

最佳解答:

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做呢種題目有個方法, 就係要令X^2前面既數相約 i.e. y=3x^2-x+1 6x^2-2x+1=2y 6x^2-2x+2-2y=0------(1) Since we need to solve 2x^2+3x-1=0 0=2x^2+3x-1 0=6x^2+9x-3-----------(2) (1)+(2): -2x+2-2y=9x-3 -11x-2y+5=0 11x+2y-5=0 So, the answer is D. (其實一眼都目弟到answer吾係A就D,因為Slope要負,MC吾夠時間可以甘撞) 希望幫到你:)

其他解答:

3x ^ 2 - x + 1 = y 6x ^ 2 - 2x + 2 = 2y 6x ^ 2 + 9x - 3 = 11x + 2y - 5 ( ∵ RHS : 2x ^ 2 +3x - 1 = 0 6x ^ 2 + 9x - 3 = 0(全行式乘三)) ∴ D is the correct answer 其實這題要你做的, 是要你將 " 3x ^ 2 - x + 1 = y " 變到好似 " 2x ^ 2 +3x - 1 = 0 "咁 所以你只要整到 " 3x ^ 2 - x + 1 = y " 的 LHS 變成 " 2x ^ 2 +3x - 1 " 的倍數便 搞掂了!4E350C6F8B48ECA2
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