Linear polynomials

Correct answer: B. \(2x-43\)

Explanation: On opening the brackets, \(4(3x-2)=12x-8\) and \(-5(2x+7)=-10x-35\). Therefore, \(12x-8-10x-35=2x-43\). Hence, the required linear polynomial is \(2x-43\). Option \(2x-27\) results from incorrectly combining the constant terms \(-8\) and \(-35\). Exam tip: When a negative coefficient multiplies a bracket, apply it to every term and check the signs carefully.

Correct answer: A. \(7x-3\)

Explanation: In \(7x-3\), the highest power of x is 1, so its degree is 1 and it is linear. \(x^2+7\) is quadratic, while \(5/x\) and \(\sqrt{x}\) are not polynomials. Exam tip: in a linear polynomial, variable powers can only be 0 or 1.

Correct answer: C. 3

Explanation: Since 4 is a zero of the polynomial, \(p(4)=0\). Thus, \(4(k+2)-20=0\), so \(4k+8=20\). Hence, \(4k=12\) and \(k=3\). If \(k=2\), then \(p(4)=4(2+2)-20=-4\), so it cannot be the required value. Exam tip: When a zero is given, substitute it for \(x\) and equate the polynomial to 0.

Correct answer: A. \(2x-21\)

Explanation: \(2p(x)-3q(x)=2(7x-3)-3(4x+5)\). On expanding, \(14x-6-12x-15=2x-21\). Hence, \(2x-21\) is the correct answer. \(2x+21\) can result from failing to distribute the negative sign in \(-3(4x+5)\) to both terms. Exam tip: when a negative coefficient multiplies a bracket, check the sign of every term carefully.

Correct answer: A. \(a=4\)

Explanation: If \(-2\) is a zero of the polynomial \((3a-4)x+16\), its value must be 0 when \(x=-2\). Thus, \((3a-4)(-2)+16=0\). This gives \(-6a+8+16=0\), or \(-6a+24=0\), so \(a=4\). For example, if \(a=2\), the polynomial evaluates to \(12\), not 0. Exam tip: Substitute the given zero into the polynomial and set the result equal to 0.

Correct answer: D. 18

Explanation: Since 6 is a zero of the polynomial, \(p(6)=0\). Therefore, \(6a+b=0\). Substituting \(a=-3\) gives \(6(-3)+b=0\), so \(b=18\). \(-18\) is a common distractor caused by missing the sign change. In exams, substitute the given zero in the polynomial and set the result equal to 0.

Correct answer: C. The condition is true for every \(c\)

Explanation: \(p(5)=9\times5+c=45+c\), while \(p(1)=9\times1+c=9+c\). Hence, \(p(1)+36=9+c+36=45+c=p(5)\). Since \(c\) occurs equally on both sides, its value cancels out; therefore, the condition holds for every \(c\). Values such as \(c=0\) and \(c=36\) are only particular cases, not requirements. Exam tip: substitute the given input values and check whether the constant term cancels.

Correct answer: D. (11x+8)

Explanation: The zero of a linear polynomial is the value of x that makes the polynomial equal to zero. For an expression of the form ax+b, solve ax+b=0, giving x=-b/a. To obtain the required zero \(-\frac{8}{11}\), the polynomial must have a positive constant 8 and coefficient 11, so that solving the equation produces a negative fraction with denominator 11.

For option D, set 11x+8=0. Subtracting 8 gives 11x=-8, and dividing by 11 gives x=-\frac{8}{11}. Thus its zero is exactly the required value. Option A would give \(\frac{8}{11}\), while the other options produce different values, so option D is correct.

Correct answer: C. (x=20)

Explanation: From (\frac{7}{10}x-14=0), (\frac{7}{10}x=14) and (x=20). With a fractional coefficient, multiply by the reciprocal.

Correct answer: A. A term with zero coefficient does not determine the degree; this is a linear polynomial

Explanation: Since \(0x^2=0\), that term contributes nothing to the polynomial. The expression becomes \(7-3x\), whose highest power is 1, so it is linear. Exam tip: first remove all terms with zero coefficients before finding degree.

Correct answer: B. \(8x-31\)

Explanation: Given \(p(x)=8x-15\), replace every \(x\) in the expression by the complete quantity \((x-2)\): \(p(x-2)=8(x-2)-15=8x-16-15=8x-31\). Hence, \(8x-31\) is correct. \(8x-17\) results from an incorrect simplification of the constant terms. Exam tip: always use brackets when substituting an expression into a function.

Correct answer: A. \(17-18x\)

Explanation: Replace x in p with the complete expression \(3x\). Thus, \(p(3x)=17-6(3x)=17-18x\). In option B, the constant term 17 is incorrectly multiplied by 3; only x is replaced by \(3x\). Exam tip: In \(p(kx)\), replace every x by \(kx\), not the constant term.

Correct answer: A. It is not a polynomial because \(\frac{2}{x}=2x^{-1}\) has a negative exponent of \(x\).

Explanation: Writing \(\frac{2}{x}=2x^{-1}\) gives an exponent of \(-1\). In a polynomial, variable exponents must be 0, 1, 2, …, so this is not linear. Exam tip: check for variables in denominators first.

Correct answer: C. Never

Explanation: From the condition \(p(6)=p(-2)\), we get \(6k+11=-2k+11\). Hence, \(8k=0\), so \(k=0\). Then \(p(x)=11\), which is a constant polynomial of degree 0, not a linear polynomial. Option A satisfies the given equality, but it does not keep the polynomial linear. Exam tip: \(ax+b\) is linear only when \(a\ne0\).

Correct answer: B. 1

Explanation: First simplify the expression: \(q(x)-2p(x)=(13x-1)-2(6x+4)=13x-1-12x-8=x-9\). The highest power of \(x\) in \(x-9\) is 1, so its degree is 1. Degree 0 would apply only to a non-zero constant polynomial; here the \(x\)-term does not cancel. Exam tip: simplify like terms before finding the degree of a sum or difference of polynomials.

Correct answer: B. \(9x-23\)

Explanation: To find the zero of the linear polynomial \(9x-23\), set it equal to zero: \(9x-23=0\). Thus, \(9x=23\), so \(x=\frac{23}{9}\). Therefore, \(9x-23\) is the correct option. The close distractor \(23x-9\) has zero \(\frac{9}{23}\), not the given value. Exam tip: the zero of \(ax+b\) is \(-\frac{b}{a}\).

Correct answer: B. \(10\)

Explanation: Given \(p(x)=10x-21\), we get \(p(x+1)=10(x+1)-21=10x-11\). Hence, \(p(x+1)-p(x)=(10x-11)-(10x-21)=10\). The option \(10x\) is incorrect because the terms containing \(x\) cancel on subtraction. Exam tip: for a linear polynomial \(ax+b\), \(p(x+1)-p(x)=a\).

Correct answer: C. (\lambda>3)

Explanation: The zero is (-\frac{18}{\lambda}). From (-\frac{18}{\lambda}>-6) and (\lambda>0), we get (\lambda>3).

Correct answer: B. The debt will be completely cleared after 8 days.

Explanation: For the zero, set \(D(n)=0\): \(600-75n=0\), so \(n=8\). Thus, the debt is cleared after 8 days. Option A describes half the debt, not zero. Exam tip: substitute 0 for the polynomial value to find its zero.

Correct answer: A. \(2x-3r\)

Explanation: \(p(x)+q(x)=(x+4r)+(x-7r)\). Combining like terms gives \(x+x=2x\) and \(4r-7r=-3r\). Therefore, the sum is \(2x-3r\). In \(2x+11r\), the signs of \(4r\) and \(-7r\) have been combined incorrectly. Exam tip: while adding polynomials, add coefficients of like terms along with their signs.

Correct answer: B. Constant polynomial

Explanation: On subtracting,
\(p(x)-q(x)=(x+4r)-(x-7r)=x+4r-x+7r=11r\). No term involving \(x\) remains, so it is a constant polynomial in \(x\). A zero polynomial would arise only if the constant itself were 0; the simplified expression is generally \(11r\). Exam tip: simplify first, then identify the highest power of the variable.

Correct answer: B. -15

Explanation: First evaluate the inner function: \(p(3)=8\times3-23=24-23=1\). Substituting this result into \(p\) again gives \(p(p(3))=p(1)=8\times1-23=-15\). Therefore, -15 is the correct option. Option 1 is only the value of \(p(3)\), not of \(p(p(3))\). Exam tip: In a composite function, always evaluate the innermost expression first.

Correct answer: C. 24

Explanation: First evaluate the inner function: \(p(0)=5\times0+4=4\). Then \(p(4)=5\times4+4=24\). Therefore, \(p(p(0))=24\). The value 20 comes from only \(5\times4\), missing the constant term 4. Exam tip: In composition questions, always evaluate the innermost function first.

Correct answer: A. \(n=\frac{3}{4}\)

Explanation: If 1 is a zero of the polynomial, its value must be 0 when \(x=1\). Thus, \((n-5)(1)+3n+2=0\), which gives \(4n-3=0\). Therefore, \(n=\frac{3}{4}\). For instance, putting \(n=1\) gives the value \(-3\), so it is not correct. Exam tip: Substitute the given zero in the polynomial and equate the result to 0.

Correct answer: C. 13

Explanation: Given \(p(x)=\frac{x}{7}+a\). Substituting \(x=21\) gives \(p(21)=\frac{21}{7}+a=3+a\). Since \(p(21)=16\), we have \(3+a=16\), so \(a=13\). Option 16 is the given value of \(p(21)\), not the value of \(a\). Exam tip: when a polynomial value is given, substitute the stated value of \(x\) first.