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For the polynomial [tex]\( P(x) = 4x^4 - 9x^2 + 8x + 2 \)[/tex] and [tex]\( c = -4 \)[/tex], find [tex]\( P(c) \)[/tex] by:

(a) Direct substitution
(b) The Remainder Theorem

(a) Find [tex]\( P(-4) \)[/tex] by direct substitution.

[tex]\[ P(-4) = \ \square \][/tex] (Type an integer.)


Sagot :

Let's begin with the task of finding [tex]\( P(-4) \)[/tex] for the polynomial [tex]\( P(x) = 4x^4 - 9x^2 + 8x + 2 \)[/tex] by direct substitution.

### Step-by-Step Solution

Step 1: Understand the polynomial and the value you need to substitute.
- The polynomial given is [tex]\( P(x) = 4x^4 - 9x^2 + 8x + 2 \)[/tex].
- We are asked to find [tex]\( P(-4) \)[/tex], so we will substitute [tex]\( x = -4 \)[/tex] into the polynomial.

Step 2: Substitute [tex]\( x = -4 \)[/tex] into the polynomial.
- Substitute [tex]\( -4 \)[/tex] for [tex]\( x \)[/tex] in each term of the polynomial:
[tex]\[ P(-4) = 4(-4)^4 - 9(-4)^2 + 8(-4) + 2 \][/tex]

Step 3: Compute each term individually.

- Calculate [tex]\((-4)^4 \)[/tex]:
[tex]\[ (-4)^4 = 256 \][/tex]
So, [tex]\( 4 \cdot 256 = 1024 \)[/tex].

- Calculate [tex]\((-4)^2 \)[/tex]:
[tex]\[ (-4)^2 = 16 \][/tex]
So, [tex]\( 9 \cdot 16 = 144 \)[/tex].

- Calculate [tex]\( 8(-4) \)[/tex]:
[tex]\[ 8 \cdot (-4) = -32 \][/tex]

- The constant term in the polynomial is [tex]\( +2 \)[/tex].

Step 4: Combine the computed values.
- Substitute the calculated values back into the polynomial expression:
[tex]\[ P(-4) = 1024 - 144 - 32 + 2 \][/tex]

Step 5: Simplify the expression.
- Perform the arithmetic step-by-step:
[tex]\[ 1024 - 144 = 880 \][/tex]
[tex]\[ 880 - 32 = 848 \][/tex]
[tex]\[ 848 + 2 = 850 \][/tex]

So, [tex]\( P(-4) = 850 \)[/tex].

### Conclusion
Therefore, by direct substitution, [tex]\( P(-4) = 850 \)[/tex].
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