9514 1404 393
Answer:
-15
Step-by-step explanation:
If 'a' and 'b' are zeros of the quadratic f(x), its factored form is ...
f(x) = (x -a)(x -b)
and its standard form is ...
f(x) = x^2 -(a+b)x +ab
This tells us that ...
a+b = -7
ab = 7
for the given quadratic.
Then the expression of interest is ...
[tex]a^{-1}+b^{-1}-2ab=\dfrac{1}{a}+\dfrac{1}{b}-2ab=\dfrac{a+b}{ab}-2ab\\\\=\dfrac{-7}{7}-2\cdot7=-1-14=\boxed{-15}[/tex]
