which property of polynomial multiplication says that the product of two polynomial is always a polynomial

  closure

Step-by-step explanation:

The property is actually a property of the set of polynomials, rather than a property of multiplication.

The set of polynomials is closed under the operation of multiplication. We call that property closure.

"standard form:

3x2 + 14x − 10 = 0

solutions based on quadratic formula:

x1   = −14 − √ 142 − 4×3×(−10) /   2×3   = −14 − 2 × √ 79 /   6   ≈ −5.296

x2   = −14 + √ 142 − 4×3×(−10) /   2×3   = −14 + 2 × √ 79 /   6   ≈ 0.629