How do you complete the square and solve #x^2+3x-28=0#?

1 Answer
smendyka
Nov 28, 2016

#x =-7# and #x = 4#

Explanation:

First, to factor the quadratic equation we need to play with integers which multiple to 28: 1,28 and 2,14 and 4,7

Trying combinations of these allows us to rewrite this problem as:

#(x + 7)(x - 4) = 0#

We can now solve for #x + 7 = 0# and #x - 4 = 0#

#x + 7 = 0 -> x + 7 - 7 = 0 - 7 -> x =-7#

#x - 4 = 0 -> x -4 + 4 = 0 + 4 -> x = 4#

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