Afamily has two cars. the first car has a fuel efficiency of 15 miles per gallon of gas and the second has a fuel efficiency of 25 miles per gallon of gas. during one particular week, the two cars went a combined total of 975 miles, for a total gas consumption of 55 gallons. how many gallons were consumed by each of the two cars that week?

15x+25y=975
x+y=55

Rearrange equation two so x is by itself.
x=-y+55

Plug the rearranged equation two into equation one.
15(-y+55)+25y=975

Evaluate the 'new' equation 1.
-15y+825+25y=975
10y+825=975
10y=150
y=15

Choose an equation to evaluate with y to get x. (i chose equation 2 because it was easier)
x+15=55

Evaluate the equation
x=55-15
x=40

So now we have x=40 and y=15

Evaluate those two terms with both equations to check the correctness.
15(40)+25(15)=975
600+375=975
975=975 (correct)

40+15=55
55=55 (correct)

Both equations are correct so the values of x and y are true.

X^2 - 4x +(4/2^2) + y^2 + 8y + (8/2^2) = -4 + (4/2^2) + (8/2^2)(x + 2)^2 + (y + 4)^2 = -4 + 4 + 16your center is (-2, -4) and the radius is the sqrt of -4 + 4 + 16 which is 4