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(d) \( x^{3}-2 x^{2}-5 x+0 \) Find the quotient and the remainder if \( f(x) \) is divisible by \( x \) (a) \( f(x)=x^{3}+3 x^{2}-x-2 ; x-2 \) (b) \( f(x)=-2 x^{4}=3 x^{2}+7 x-26 ; x+3 \) (c) \( f(x)=4 x^{3}-2 x^{2}-5 x+1 ; x-2 / 3 \)

Ask by Wilson Ruiz. in Ghana
Mar 10,2025

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Answer

**(a) Quotient:** \( x^2 + 5x + 9 \), **Remainder:** 16 **(b) Quotient:** \( -2x^3 + 6x^2 - 15x + 52 \), **Remainder:** -182 **(c) Quotient:** \( 4x^2 + \frac{2}{3}x - \frac{41}{9} \), **Remainder:** \(-\frac{55}{27}\) **(d) Quotient:** \( x^2 - 2x - 5 \), **Remainder:** 0

Solution

**(a) Divide \( f(x)=x^{3}+3x^{2}-x-2 \) by \( x-2 \):** Write the polynomial with coefficients: \(1\) (for \(x^3\)), \(3\) (for \(x^2\)), \(-1\) (for \(x\)), and \(-2\) (constant). Using synthetic division with \( r=2 \) (since \( x-2=0 \) gives \( x=2 \)): 1. Bring down the first coefficient: \(1\). 2. Multiply by \(2\): \(1 \times 2 = 2\). 3. Add to the next coefficient: \(3 + 2 = 5\). 4. Multiply: \(5 \times 2 = 10\). 5. Add to the next coefficient: \(-1 + 10 = 9\). 6. Multiply: \(9 \times 2 = 18\). 7. Add to the constant: \(-2 + 18 = 16\). Thus, the quotient is \[ x^2+5x+9 \] and the remainder is \[ 16. \] --- **(b) Divide \( f(x)=-2x^4+3x^2+7x-26 \) by \( x+3 \):** First, write the polynomial in full degree order (note the missing \( x^3 \) term): \[ -2x^4+0x^3+3x^2+7x-26. \] We use synthetic division with \( r=-3 \) (since \( x+3=0 \) gives \( x=-3 \)): Coefficients: \(-2\), \(0\), \(3\), \(7\), \(-26\). 1. Bring down \(-2\). 2. Multiply: \(-2 \times (-3) = 6\). 3. Add: \(0 + 6 = 6\). 4. Multiply: \(6 \times (-3) = -18\). 5. Add: \(3 + (-18) = -15\). 6. Multiply: \(-15 \times (-3) = 45\). 7. Add: \(7 + 45 = 52\). 8. Multiply: \(52 \times (-3) = -156\). 9. Add: \(-26 + (-156) = -182\). The quotient becomes \[ -2x^3+6x^2-15x+52 \] and the remainder is \[ -182. \] --- **(c) Divide \( f(x)=4x^3-2x^2-5x+1 \) by \( x-\frac{2}{3} \):** We use synthetic division with \( r=\frac{2}{3} \) (since \( x-\frac{2}{3}=0 \) gives \( x=\frac{2}{3} \)). Coefficients: \(4\), \(-2\), \(-5\), \(1\). 1. Bring down \(4\). 2. Multiply: \(4 \times \frac{2}{3} = \frac{8}{3}\). 3. Add: \(-2 + \frac{8}{3} = -\frac{6}{3}+\frac{8}{3} = \frac{2}{3}\). 4. Multiply: \(\frac{2}{3} \times \frac{2}{3} = \frac{4}{9}\). 5. Add: \(-5 + \frac{4}{9} = -\frac{45}{9}+\frac{4}{9} = -\frac{41}{9}\). 6. Multiply: \(-\frac{41}{9} \times \frac{2}{3} = -\frac{82}{27}\). 7. Add: \(1 + \left(-\frac{82}{27}\right) = \frac{27}{27}-\frac{82}{27} = -\frac{55}{27}\). Thus, the quotient is \[ 4x^2 + \frac{2}{3}x - \frac{41}{9} \] and the remainder is \[ -\frac{55}{27}. \] --- **(d) Divide \( f(x)=x^3-2x^2-5x \) by \( x \):** Since the divisor is \( x \), divide each term by \( x \): \[ \frac{x^3}{x} = x^2,\quad \frac{-2x^2}{x} = -2x,\quad \frac{-5x}{x} = -5. \] Thus, we have \[ x^3-2x^2-5x = x\left(x^2-2x-5\right). \] The quotient is \[ x^2-2x-5, \] and since the division is exact, the remainder is \[ 0. \]

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To find the quotient and the remainder with respect to \( x \) for the polynomial \( f(x) = x^{3}-2 x^{2}-5 x \), we first divide it by \( x \). Since polynomial division by \( x \) is straightforward, we can see that the quotient is simply the polynomial \( f(x) \) divided by \( x \), which leaves us with: Quotient: \( x^{2}-2 x-5 \) Remainder: \( 0 \) (since \( f(x) \) is divisible by \( x \)). Now, let's explore the real-world application of polynomial functions. Polynomials are used extensively in economics to model cost and revenue functions. For instance, a business could represent its profit in terms of the number of units sold—with polynomial equations allowing for adjustments in price to reflect production costs. The resulting curves can help companies predict how changes in price or production affect their bottom line! In any polynomial division, always check your work! Common mistakes include overlooking the signs when bringing down terms or incorrectly applying the long division process. Always remember to align like terms correctly and verify your quotient by multiplying it back with the divisor. It’s a great way to catch any errors before finalizing your answer!

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