DWG3-15

[JS]

Q15:
If x ≠ 0, then (x + 1/x)2 - (x - 1/x)2 =

A. 1/x
B. x
C. 1
D. 2
E. 4

Ans: E

I try it so many times and always get the answer 4/x. what's wrong with me?? help pls!!

[DARY]

Q15:
If x ≠ 0, then (x + 1/x)2 - (x - 1/x)2 =

A. 1/x
B. x
C. 1
D. 2
E. 4

Ans: E

I try it so many times and always get the answer 4/x. what's wrong with me?? help pls!!

(x + 1/x)^2 - (x - 1/x)^2 才對
展開來算就好了

[JS]

Trust me, I am a complete math idiot
So, can you be so kind and tell me what I did wrong here.

(x + 1/x)^2 - (x - 1/x)^2
= (x+1/x –( x-1/x) (x+1/x + x-1/x)
= 2/x . 2x/x
= 4/x

Help!

[DARY]

Trust me, I am a complete math idiot
So, can you be so kind and tell me what I did wrong here.

(x + 1/x)^2 - (x - 1/x)^2
= (x+1/x –( x-1/x) (x+1/x + x-1/x)
= 2/x . 2x/x
= 4/x

Help!

問題出在紅色的地方

括號裡面的分母只屬於後面那一項
(x+1/x)=(x)+(1/x)
並不是(x+1)/x，要看清楚喔

[JS]

I can't be.... this is ri..... oh my........(fainted)......

[chris8888]

If x ≠ 0, then ((x)+ (1/x))^2 - ((x) - (1/x))^2 =

A. 1/x
B. x
C. 1
D. 2
E. 4

Ans: E

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