Ducks have 1 head. Dogs have 1 head.
Ducks have 2 feet. Dogs have 4 feet.
If x = no. of ducks and g = no. of dogs
x + g = 25
2x + 4g = 80
Let's use substitution to solve.
x + g = 25 ⇒ x = 25 - g
replace x with 25 - g in the other equation and solve for g
2x + 4g = 80
2(25 - g) + 4g = 80
50 - 2g + 4g = 80
50 + 2g = 80
2g = 30
g = 15
Now use g = 15 in an earlier equation to find x.
x + g = 25
x + 15 = 25
x = 10
F(x) = x² + 4x - 12
x = -b/2a
x = -(4)/2(1)
x = -4/2
x = 2
f(x) = x² + 4x - 12
f(2) = (2)² + 4(2) - 12
f(2) = 4 + 8 - 12
f(2) = 12 - 12
f(2) = 0
The vertex of the function is (2,0).
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