Q. \((x-1)(x^2+3x-5)\).
Answer
Problem: Expand the expression to a polynomial in standard form: left parenthesis, x, minus, 1, right parenthesis, left parenthesis, x, squared, plus, 3, x, minus, 5, right parenthesis (x−1)(x 2 +3x−5)
Multiply and combine like terms:
\[
(x-1)(x^2+3x-5)=x(x^2+3x-5)-1(x^2+3x-5)
\]
\[
= x^3+3x^2-5x -x^2-3x+5 = x^3+2x^2-8x+5.
\]
Final result: \(\;x^3+2x^2-8x+5.\)
Detailed Explanation
Problem: Expand the product \( (x-1)(x^2+3x-5) \).
- Step 1 — Apply the distributive property (multiply each term of the second polynomial by each term of the first):Write the product as a sum of two products:
\( (x-1)(x^2+3x-5) = x\,(x^2+3x-5) – 1\,(x^2+3x-5) \). - Step 2 — Multiply the first term \(x\) by each term of the second polynomial:Compute:
\( x\cdot x^2 = x^3 \),
\( x\cdot 3x = 3x^2 \),
\( x\cdot (-5) = -5x \).So \( x\,(x^2+3x-5) = x^3 + 3x^2 – 5x \).
- Step 3 — Multiply the second term \(-1\) by each term of the second polynomial:Compute:
\( -1\cdot x^2 = -x^2 \),
\( -1\cdot 3x = -3x \),
\( -1\cdot (-5) = +5 \).So \( -1\,(x^2+3x-5) = -x^2 – 3x + 5 \).
- Step 4 — Add the two results and combine like terms:Sum:
\( (x^3 + 3x^2 – 5x) + (-x^2 – 3x + 5) \).Group like terms:
Cubic term: \( x^3 \).
Quadratic terms: \( 3x^2 + (-x^2) = 2x^2 \).
Linear terms: \( -5x + (-3x) = -8x \).
Constant term: \( 5 \).Thus the combined result is
\( x^3 + 2x^2 – 8x + 5 \). - Final Answer:\( x^3 + 2x^2 – 8x + 5 \)
See full solution
FAQs
How do I expand \( (x-1)(x^2+3x-5) \)?.
Distribute: \(x(x^2+3x-5)-1(x^2+3x-5)=x^3+3x^2-5x-x^2-3x+5\). Combine like terms to get \(x^3+2x^2-8x+5\).
What is the polynomial in standard form?
Standard form orders powers descending: \(x^3+2x^2-8x+5\).
How can I check my expansion is correct?
Evaluate both expressions at a few \(x\)-values (e.g., \(x=0,1,2\)). If they match for several values, the expansion is correct. Alternatively, expand symbolically and compare.
What is the degree and leading coefficient?
The degree is 3 and the leading coefficient is 1 (from \(x^3\)).
What are the zeros of the polynomial?.
Solve \(x-1\)(\(x^2+3x-5\))\(=0\). One root is \(x=1\); the quadratic gives \(x=\frac{-3\pm\sqrt{29}}{2}\).
Can the polynomial be factored further over the rationals?
Can the polynomial be factored further over the rationals?
What is a quick method to multiply expressions like this?
Use the distributive property: multiply each term of the first factor by each term of the second, then combine like terms. For binomial×trinomial do three multiplications and sum.
What is the \(y\)-intercept of the polynomial?
Set \(x=0\): \(y=5\). The y-intercept is \( (0,5)\).
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