Find the value of [tex]\( k \)[/tex] if [tex]\( 5x^4 + 2kx^3 - 6kx^2 + 9 \)[/tex] has a remainder of 22 when divided by [tex]\( x-1 \)[/tex].



Answer :

Sure, let's find the value of [tex]\( k \)[/tex] such that the polynomial [tex]\( 5x^4 + 2kx^3 - 6kx^2 + 9 \)[/tex] has a remainder of 22 when divided by [tex]\( x - 1 \)[/tex].

### Step-by-Step Solution:

1. Determine the Remainder Using Polynomial Division:
When a polynomial [tex]\( P(x) \)[/tex] is divided by [tex]\( x - a \)[/tex], the remainder is given by [tex]\( P(a) \)[/tex]. Here, [tex]\( a = 1 \)[/tex], so we need to find [tex]\( P(1) \)[/tex].

2. Evaluate the Polynomial [tex]\( P(x) = 5x^4 + 2kx^3 - 6kx^2 + 9 \)[/tex] at [tex]\( x = 1 \)[/tex]:
Let's substitute [tex]\( x = 1 \)[/tex] into the polynomial.
[tex]\[ P(1) = 5(1)^4 + 2k(1)^3 - 6k(1)^2 + 9 \][/tex]
Simplifying this,
[tex]\[ P(1) = 5 + 2k - 6k + 9 \][/tex]
Combine the like terms:
[tex]\[ P(1) = 5 + 9 + 2k - 6k \][/tex]
Simplify further:
[tex]\[ P(1) = 14 - 4k \][/tex]

3. Given that the remainder is 22:
Since the remainder when the polynomial is divided by [tex]\( x - 1 \)[/tex] is 22,
[tex]\[ P(1) = 22 \][/tex]

4. Set up the equation and solve for [tex]\( k \)[/tex]:
We have
[tex]\[ 14 - 4k = 22 \][/tex]
Subtract 14 from both sides:
[tex]\[ -4k = 22 - 14 \][/tex]
Simplify the right-hand side:
[tex]\[ -4k = 8 \][/tex]

5. Solve for [tex]\( k \)[/tex]:
Divide both sides by -4:
[tex]\[ k = \frac{8}{-4} = -2 \][/tex]

### Conclusion:

The value of [tex]\( k \)[/tex] that satisfies the condition is:
[tex]\[ \boxed{-2} \][/tex]