Use the remainder theorem to determine if the given number [tex]\( c \)[/tex] is a zero of the polynomial.

[tex]\[ f(x) = 2x^4 + 7x^3 - 18x^2 + 4x + 95 \][/tex]

Part 1 of 2
(a) [tex]\( c = -5 \)[/tex]

Is [tex]\( c = -5 \)[/tex] a zero of the polynomial? [tex]\(\square\)[/tex] (Choose one)

Part 2 of 2
(b) [tex]\( c = 6 \)[/tex]

Is [tex]\( c = 6 \)[/tex] a zero of the polynomial? [tex]\(\square\)[/tex] (Choose one)



Answer :

To determine if the given number [tex]\( c \)[/tex] is a zero of the polynomial [tex]\( f(x) = 2x^4 + 7x^3 - 18x^2 + 4x + 95 \)[/tex], we will employ the Remainder Theorem. The Remainder Theorem states that if a polynomial [tex]\( f(x) \)[/tex] is divided by [tex]\( x - c \)[/tex], the remainder of this division is [tex]\( f(c) \)[/tex]. If [tex]\( f(c) = 0 \)[/tex], then [tex]\( c \)[/tex] is a zero of the polynomial.

### Part 1: [tex]\( c = -5 \)[/tex]
1. Evaluate the polynomial at [tex]\( c = -5 \)[/tex]:
[tex]\[ f(-5) = 2(-5)^4 + 7(-5)^3 - 18(-5)^2 + 4(-5) + 95 \][/tex]

2. Calculate each term individually:
[tex]\[ 2(-5)^4 = 2 \cdot 625 = 1250 \][/tex]
[tex]\[ 7(-5)^3 = 7 \cdot (-125) = -875 \][/tex]
[tex]\[ -18(-5)^2 = -18 \cdot 25 = -450 \][/tex]
[tex]\[ 4(-5) = -20 \][/tex]
[tex]\[ 95 \text{ (constant term)} = 95 \][/tex]

3. Sum these values:
[tex]\[ f(-5) = 1250 - 875 - 450 - 20 + 95 = 0 \][/tex]

Since [tex]\( f(-5) = 0 \)[/tex], [tex]\( c = -5 \)[/tex] is a zero of the polynomial.

(a) [tex]\( c = -5 \)[/tex] is a zero of the polynomial.

### Part 2: [tex]\( c = 6 \)[/tex]
1. Evaluate the polynomial at [tex]\( c = 6 \)[/tex]:
[tex]\[ f(6) = 2(6)^4 + 7(6)^3 - 18(6)^2 + 4(6) + 95 \][/tex]

2. Calculate each term individually:
[tex]\[ 2(6)^4 = 2 \cdot 1296 = 2592 \][/tex]
[tex]\[ 7(6)^3 = 7 \cdot 216 = 1512 \][/tex]
[tex]\[ -18(6)^2 = -18 \cdot 36 = -648 \][/tex]
[tex]\[ 4(6) = 24 \][/tex]
[tex]\[ 95 \text{ (constant term)} = 95 \][/tex]

3. Sum these values:
[tex]\[ f(6) = 2592 + 1512 - 648 + 24 + 95 = 3575 \][/tex]

Since [tex]\( f(6) \neq 0 \)[/tex], [tex]\( c = 6 \)[/tex] is not a zero of the polynomial.

(b) [tex]\( c = 6 \)[/tex] is not a zero of the polynomial.