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Given the expression -x^2-6x+7,when expressed in form a(x+h)^2+k, the value of k is?​

User Kassan
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1 Answer

10 votes

Answer: k = 16

Explanation:

The equation is written in the form:

y = ax^2 + bx + c

y = -x^2 - 6x + 7

y = a(x - h)^2 + k where (h, k) is the vertex

a = -1 (from the original equation)

h = -b/2a (this is the equation for the line of symmetry or the x-value of the vertex)

h = -(-6)/2(-1) = 6/-2 = -3

when x = -3, y = ?

y = -(-3)^2 - 6(-3) + 7

y = -(9) + 18 + 7

y = -9 + 18 + 7

y = 16

(-3, 16) is the vertex

Since k is the y-value of the vertex, k = 16

I'll just take it a step further and write the whole equation:

Substitute all the values we found

-1(x +3)^2 + 16

-(x + 3)^2 + 16

User Martin Wunderlich
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