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what is the equation of a quadratic function with roots -1 and -7 and a vertex at (-4, 7)?
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y = -14/9(x + 4)^2 + 7

Step-by-step explanation:

The given roots of the quadratic function is (-1, -7)

The vertex is at (-4, 7)

The formula is

y = a(x - h)^2 + k

The vertex is (h, k)

Comparing with the given vertex, (-4, 7), h = -4 and k = 7

Substituting into the formula

y = a(x - h)^2 + k, it becomes

y = a(x - - 4)^2 + 7

y = a(x + 4)^2 + 7

From the roots given (-1, -7)

x = -1 and y = -7

Substituting x = -1 and y = -7 into the equation,

y = a(x + 4)^2 + 7, it becomes

-7 = a(-1+4)^2 + 7

-7 = a(3^2 ) + 7

- 7 = 9a + 7

-7-7 = 9a

9a = -14

a = -14/9

Substituting a = - 14/9 into the equation, it becomes

y = -14/9(x + 4)^2 + 7

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.