Q. It is given that 10x3+5x2−x+4=(2x−1)(x+3)Q(x)+Ax+B, where Q(x) is a polynomial. Find the values of the constants A and B.
Understand Polynomial Division: Understand the division of polynomials.The given equation is a polynomial division where the dividend is 10x3+5x2−x+4 and the divisor is (2x−1)(x+3). The quotient is Q(x) and the remainder is Ax+B. To find A and B, we need to perform polynomial long division or synthetic division.
Set Up Division: Set up the division.Since Q(x) is a polynomial and we are given that the remainder is linear (of the form Ax+B), we can infer that Q(x) must be of degree 1 (since the degree of the dividend is 3 and the divisor is 2). Let's denote Q(x)=Cx+D where C and D are constants to be determined.
Multiply Divisor by Quotient: Multiply the divisor by the assumed quotient.We multiply (2x−1)(x+3) by Q(x)=Cx+D to get the part of the dividend that is divisible by the divisor.(2x−1)(x+3)(Cx+D)=(2Cx2+(6C−D)x−D)(x+3)Now we expand this product to find the coefficients that will match the dividend.
Expand and Equate Coefficients: Expand the product and equate coefficients.Expanding the product, we get:2Cx3+(6C−D)x2−Dx+2Cx2+(6C−D)x−DCombining like terms, we have:2Cx3+(6C−D+2C)x2+(6C−D−D)x−DThis simplifies to:2Cx3+(8C−D)x2+(6C−2D)x−DNow we equate the coefficients of this expression to the coefficients of the dividend 10x3+5x2−x+4.
Equate x^3 Coefficients: Equate the coefficients of the x^3 terms.From the x^3 terms, we have:2C=10Solving for C, we get:C=5
Equate x^2 Coefficients: Equate the coefficients of the x^2 terms.From the x^2 terms, we have:8C−D=5Substituting C=5 into this equation, we get:8(5)−D=5Solving for D, we get:40−D=5D=40−5D=35
Realize and Correct Mistake: Realize the mistake and correct it.We made a mistake in the previous step. We should have equated the coefficients of the x^2 terms to the dividend's x^2 coefficient, which is 5. However, we incorrectly equated 8C−D to 5 instead of 8C−D to the dividend's x^2 coefficient. Let's correct this.
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