Answer:
[tex]-\frac{1}{7}[/tex]
Step-by-step explanation:
When given the following expression,
[tex]\frac{a+c}{a^2-c^2}[/tex]
With the information that the values (a = -2) and (c = 5), one is asked to evaluate the expression. One's first instinct is probably to substitute the values into the expression and solve, however, a faster approach is to simplify the expression. The denominator is the difference of squares, thus one can rewrite it as the product of two linear expressions. Then one can simplify it by canceling out like terms in the denominator and the numerator. Finally, one can then substitute the values of the (a) and (c) into the simplified expression and solve.
[tex]\frac{a+c}{a^2-c^2}[/tex]
[tex]=\frac{a+c}{(a+c)(a-c)}[/tex]
Cross out like terms in the numerator and denominator,
[tex]=\frac{a+c}{(a+c)(a-c)}[/tex]
[tex]=\frac{1}{a-c}[/tex]
Now substitute the values of (a) and (c) into the expression and simplify to evaluate,
[tex]=\frac{1}{a-c}[/tex]
[tex]=\frac{1}{(-2)-(5)}\\\\=\frac{1}{-2-5}\\\\=-\frac{1}{7}[/tex]
