Question

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Answer 1

1. (m+10-(n-12))*(m+10+(n-12))
    (m+10-n+12)*(m+10+n-12)
    (m+22-n)*(m-2+n)
2. (c+19d-(19c+d))*(c+19d+(19c+d))
    (c+19d-19c-d)*(c+19d+19c+d)
    (-18(c-d))*20(c+d)
    -18*20(c-d)*(c+d)
    -360(c-d)*(c+d)
3. $(a+b+c)^{2}= a^{2}+ b^{2}+ c^{2}+2ab+2ac+2bc$