Solve the Problem $f ( x , y ) = \int _ { x } ^ { y } t d t$

Multiple Choice

Solve the problem.
-Find an equation for the level curve of the function $f ( x , y ) = \int _ { x } ^ { y } t d t$ that passes through the point $( 6,9 )$ .

A) $y ^ { 2 } - x ^ { 2 } = 117$
B) $y ^ { 2 } - x ^ { 2 } = - 45$
C) $y ^ { 2 } - x ^ { 2 } = 45$
D) $y ^ { 2 } + x ^ { 2 } = 117$