Q. Given P(x)=3x4−2x3−x2−12x−4, write P(x) as a product of linear factors. (3.4/3.5)P(x)=(3x+1)(x−2)(x−(−21+27i))(x−(−21−27i))
Identify Possible Rational Roots: To factor the polynomial P(x)=3x4−2x3−x2−12x−4, we first look for any rational roots using the Rational Root Theorem. The possible rational roots are the factors of the constant term −4 divided by the factors of the leading coefficient 3.
Test x=1: The factors of −4 are ±1, ±2, ±4, and the factors of 3 are ±1, ±3. So the possible rational roots are ±1, ±31, ±2, −41, ±4, −43. We can test these roots by direct substitution into the polynomial or by using synthetic division.
Test x=−1: Let's test x=1: P(1)=3(1)4−2(1)3−(1)2−12(1)−4=3−2−1−12−4=−16, which is not zero. So x=1 is not a root.
Test x=2: Let's test x=−1: P(−1)=3(−1)4−2(−1)3−(−1)2−12(−1)−4=3+2−1+12−4=12, which is not zero. So x=−1 is not a root.
Perform Polynomial Division: Let's test x=2: P(2)=3(2)4−2(2)3−(2)2−12(2)−4=3×16−2×8−4−24−4=48−16−4−24−4=0. So x=2 is a root.
Use Synthetic Division: Now that we have found a root, x=2, we can perform polynomial division or use synthetic division to divide P(x) by (x−2) to find the other factors.
Factor the Cubic Polynomial: Using synthetic division with the root x=2, we divide P(x) by (x−2) and get a quotient of 3x3+4x2−9x−2.
Test x=−1: We now need to factor the cubic polynomial 3x3+4x2−9x−2. We can again use the Rational Root Theorem to find possible rational roots for this cubic polynomial.
Test x=−31: The possible rational roots for the cubic polynomial are the same as before: ±1, ±31, ±2, ±32, ±4, ±34. We test these roots by direct substitution or synthetic division.
Test x=−31: Let's test x=−1: The cubic polynomial evaluated at x=−1 gives 3(−1)3+4(−1)2−9(−1)−2=−3+4+9−2=8, which is not zero. So x=−1 is not a root.
Test x=−31: Let's test x=−1: The cubic polynomial evaluated at x=−1 gives 3(−1)3+4(−1)2−9(−1)−2=−3+4+9−2=8, which is not zero. So x=−1 is not a root.Let's test x=−31: The cubic polynomial evaluated at x=−31 gives 3(−31)3+4(−31)2−9(−31)−2=−91+94+3−2=91+912−918=−95, which is not zero. So x=−31 is not a root.
Test x=−31: Let's test x=−1: The cubic polynomial evaluated at x=−1 gives 3(−1)3+4(−1)2−9(−1)−2=−3+4+9−2=8, which is not zero. So x=−1 is not a root.Let's test x=−31: The cubic polynomial evaluated at x=−31 gives 3(−31)3+4(−31)2−9(−31)−2=−91+94+3−2=91+912−918=−95, which is not zero. So x=−31 is not a root.Let's test x=−31 again, but this time more carefully. The cubic polynomial evaluated at x=−31 gives x=−11, which simplifies to x=−12. This is not zero, so x=−31 is indeed not a root.
More problems from Find derivatives of using multiple formulae