Three integers have a negative product. If multiplying this product by two other integers results in a positive product, then the other two integers must have the same sign.
Proof: Let a,b,c be the three integers with negative product. If ab(c)(d)(e)>0, then d and e must have the same sign.
Martha wrote a quadratic function f(x)=5x3+2x2+7x−3. Two corrections: 1) Eliminate the 5x3 term, 2) Change the exponent of 2x2 to 3 and combine with 5x3.