Let $f ( x , y ) = x + 2 y$ . Then $f ( x , y + \Delta y ) - f ( x , y )$ is

A) $\Delta x - 2 \Delta y$
B) $\Delta y$
C) $2 \Delta y$
D) $x + 2 \Delta y$
E) $\Delta x + 2 \Delta y$

Name: Let $f ( x , y ) = x + 2 y$ . Then $f ( x , y + \Delta y ) - f ( x , y )$ is A) $\Delta x - 2 \Delta y$ B) $\Delta y$ C) $2 \Delta y$ D) $x + 2 \Delta y$ E) $\Delta x + 2 \Delta y$
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Question

Let $f ( x , y ) = x + 2 y$ . Then $f ( x , y + \Delta y ) - f ( x , y )$ is

A) $\Delta x - 2 \Delta y$
B) $\Delta y$
C) $2 \Delta y$
D) $x + 2 \Delta y$
E) $\Delta x + 2 \Delta y$

Quizplus · Accepted Answer

$f(x, y + \Delta y) = x + 2(y + \Delta y) = x + 2y + 2\Delta y$. Subtracting $f(x, y) = x + 2y$ from this gives $2\Delta y$.

Let f(x,y)=x+2yf ( x , y ) = x + 2 yf(x,y)=x+2y

Let $f ( x , y ) = x + 2 y$