+2669 Fill in the blank with a constant, so that the resulting expression can be factored as the product of two linear expressions:
2mn - 21m + 6n + mn - 9m + ___
+399 \(3mn-30m+6n+c\)
\(3m(n - 10) + 6n + c\)
\(3m(n-10)+6(n-10)+60+c\)
\((3m+6)(n-10)+60+c\)
\(c+60 = 0\)
\(c=-60\)
The constant is -60.
+399 \(3mn-30m+6n+c\)
\(3m(n - 10) + 6n + c\)
\(3m(n-10)+6(n-10)+60+c\)
\((3m+6)(n-10)+60+c\)
\(c+60 = 0\)
\(c=-60\)
The constant is -60.
