If (a,-3) is a point on the graph of y=x^2+4x, what is the value of a?

Question

so far i have -3=x^2+4x

i can do the problem on my graphing calc but we can't use a graphing calc on the test so i need to know how to do it by hand. what do i do next?

Answer 1

your equation would be
-3 = a^2 + 4a
a^2 + 4a + 3 = 0
(a+1)(a+3) = 0
a = -1 or a = -3

Answer 2

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