Math

Question Find the degree 4 polynomial P(x)P(x) with roots at x=4x=4 (multiplicity 2), x=0x=0 (multiplicity 1), and x=2x=-2 (multiplicity 1), passing through (1,135)(1,-135).

Studdy Solution

STEP 1

Assumptions
1. The polynomial P(x)P(x) is of degree 44.
2. P(x)P(x) has a root of multiplicity 22 at x=4x=4.
3. P(x)P(x) has roots of multiplicity 11 at x=0x=0 and x=2x=-2.
4. P(x)P(x) passes through the point (1,135)(1, -135).

STEP 2

The general form of a polynomial with the given roots can be written as:
P(x)=a(xr1)n1(xr2)n2...(xrk)nkP(x) = a(x - r_1)^{n_1}(x - r_2)^{n_2}...(x - r_k)^{n_k}
where aa is a leading coefficient, rir_i are the roots, and nin_i are their multiplicities.

STEP 3

Since we know the roots and their multiplicities, we can write P(x)P(x) as:
P(x)=a(x4)2(x0)(x+2)P(x) = a(x - 4)^2(x - 0)(x + 2)

STEP 4

Expand the polynomial to find a general expression for P(x)P(x):
P(x)=a(x28x+16)(x)(x+2)P(x) = a(x^2 - 8x + 16)(x)(x + 2)

STEP 5

Continue expanding the polynomial:
P(x)=a(x38x2+16x)(x+2)P(x) = a(x^3 - 8x^2 + 16x)(x + 2)

STEP 6

Finish expanding the polynomial:
P(x)=a(x48x3+16x2+2x316x2+32x)P(x) = a(x^4 - 8x^3 + 16x^2 + 2x^3 - 16x^2 + 32x)

STEP 7

Combine like terms:
P(x)=a(x46x3+48x)P(x) = a(x^4 - 6x^3 + 48x)

STEP 8

Now we use the point (1,135)(1, -135) to find the leading coefficient aa. We plug in x=1x = 1 and P(x)=135P(x) = -135:
135=a(14613+481)-135 = a(1^4 - 6 \cdot 1^3 + 48 \cdot 1)

STEP 9

Simplify the equation:
135=a(16+48)-135 = a(1 - 6 + 48)

STEP 10

Further simplify the equation:
135=a(43)-135 = a(43)

STEP 11

Solve for aa:
a=13543a = \frac{-135}{43}

STEP 12

Now that we have the value of aa, we can write the final formula for P(x)P(x):
P(x)=13543(x46x3+48x)P(x) = \frac{-135}{43}(x^4 - 6x^3 + 48x)
This is the formula for the polynomial P(x)P(x) that satisfies all the given conditions.

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