How much does f(x,y)=8-2x+3y change by if x increases by 1 and y increases by 4?

Answer 1

f(x,y) = 8-2x +3y, x increases by 1 and y increases by 4

try a specific example, say x=1, y=1

then f(1,1) = 8-2+3 = 9

and

f(2,5) = 8-4+15 = 19

that shows f(x,y) increased by 10, from 9 to 19,

try another example, x=2,y=4

f(2,4) = 8-4+12 = 16

f(3,8) = 8-6+24 = 26

that's an increase by 10 again, from 16 to 26

Go with 10

unlikely that's just a coincidence

ignore the 8

look at the -2x+3y

if x=y=0, then -2x+3y= 0

increase x by 1 and y by 4,

then -2x+3y= -2(1)+3(4) =-2+12 = 10