Jack wrote the following: (x+1)^2 - (x+2)(x-3) = x^2 + 2x+1-x^2-x-6 = x-5. What mistakes did he make? write a correct simplification and explain how to avoid making this error.
We can see how he didn't distribute the negative sign in -(x^2-x-6) to the -x and -6.
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