Re: If x+y different from zero , which of the following is a solution
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02 Mar 2026, 03:11
The Logic: Simplification without Traps
1. Start with the original inequality:
$$
\(\frac{x^2-y^2-1}{x+y}>\frac{-1}{x+y}\)
$$
2. Move everything to one side:
Subtract $\(\frac{-1}{x+y}\)$ from both sides to set the inequality to zero:
$$
\(\frac{x^2-y^2-1}{x+y}+\frac{1}{x+y}>0\)
$$
3. Combine the fractions:
Since the denominators are the same, combine the numerators:
$$
\(\frac{x^2-y^2-1+1}{x+y}>0 \Rightarrow \frac{x^2-y^2}{x+y}>0\)
$$
4. Factor the numerator:
Recall the difference of squares: $\(x^2-y^2=(x-y)(x+y)\)$.
$$
\(\frac{(x-y)(x+y)}{x+y}>0\)
$$
5. Cancel the common term:
The problem states $\(x+y \neq 0\)$, so we can safely cancel the ( $\(x+y\)$ ) terms.
Note: Regardless of whether $\(x+y\)$ is positive or negative, the fraction simplifies to:
$$
\(x-y>0\)
$$
Or, simply: $\(x>y\)$
Checking the Options $(x>y)$ :
- A. $\(x=3, y=7: 3>7\)$ (False)
- B. $\(x=-3, y=7:-3>7\)$ (False)
- C. $\(x=-11, y=-9:-11>-9\)$ (False)
- D. $\(x=9, y=-6: 9>-6\)$ (True)
- E. $\(x=-20, y=-24:-20>-24\)$ (True)
- F. $\(x=12, y=9: 12>9\)$ (True)
- G. $\(x=-2, y=16:-2>16\)$ (False)
Correct Solutions:
D, E, and F