Q. \((x-4)(2x^2+5x-3)\)
Answer
Use distributive law (multiply each term of the quadratic by x and by −4):
\[
(x-4)(2x^2+5x-3)=x(2x^2+5x-3)-4(2x^2+5x-3)
\]
\[
=2x^3+5x^2-3x-8x^2-20x+12
\]
\[
=2x^3-3x^2-23x+12.
\]
Final result: \(\;2x^3-3x^2-23x+12.\)
Detailed Explanation
Problem: Multiply and simplify \( (x-4)(2x^2+5x-3) \).
- Distribute \(x\) across the trinomial:
\(x\cdot(2x^2+5x-3)=2x^3+5x^2-3x\). - Distribute \(-4\) across the trinomial:
\(-4\cdot(2x^2+5x-3)=-8x^2-20x+12\). - Add the results and combine like terms:
\[
(2x^3+5x^2-3x)+(-8x^2-20x+12)
=2x^3+(5x^2-8x^2)+(-3x-20x)+12
=2x^3-3x^2-23x+12.
\]
Final answer: \(\displaystyle 2x^3-3x^2-23x+12\)
FAQs
How do I expand \( (x-4)(2x^2+5x-3) \)?
Multiply and combine like terms: \(x(2x^2+5x-3)-4(2x^2+5x-3)=2x^3-3x^2-23x+12\).
How do I factor \(2x^2+5x-3\) and factor the whole expression completely?
Factor the quadratic: \(2x^2+5x-3=(2x-1)(x+3)\). So the full factorization is \((x-4)(2x-1)(x+3)\).
What are the zeros / x-intercepts of the polynomial?
Set each factor to zero: \(x=4, x=\frac{1}{2}, x=-3\).
What is the degree and leading coefficient of the expanded polynomial?
Degree is 3 (cubic). Leading coefficient is 2, so the polynomial is \(2x^3-3x^2-23x+12\).
What is the y-intercept?
Evaluate at \(x=0\): \(y=12\). So the y-intercept is \((0,12)\).
What is the end behavior of the graph?
What is the end behavior of the graph?
Can I use synthetic division with \(x-4\)?
Yes. Synthetic division by 4 on \(2x^3-3x^2-23x+12\) gives quotient \(2x^2+5x-3\) and remainder 0, confirming \(x-4\) is a factor.
What are the multiplicities of the roots?
Each root \(4, \frac{1}{2}, -3\) has multiplicity 1, so the graph crosses the x-axis at each zero.
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