You can put this solution on YOUR website! Solve by completing the square.
x2 – 2x – 15 = 0
x^2-2x-15+15=0+15
x^2-2x+___=15+___
fill the blank with (b/2)^2 (b is the coefficient of x)
x^2-2x+(-2/2)^2=15+(-2/2)^2
x^2-2x+(-1)^2=15+(-1)^2
x^2-2x+1=15+1
x^2-2x+1=16
Now you have a perfect square trinomial that can be factored like this.
(x-1)^2=16
x-1=+/-4
x-1+1=1+/-4
x=1+/-4
x=1-4 or x=1+4
x=-3 or x=5
Happy Calculating!!!
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