if the zeros of the polynomial x cube minus 3 X square + X + 1 hour a minus b, a, a + b, find a and
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3
Answer:
a = 1 and b = ±√2.
The roots are 1, 1-√2 and 1+√2.
Step-by-step explanation:
For a cubic
Ax³ + Bx² + Cx + D
the sum of the roots is -B/A and the product of the roots is -D/A.
So for the cubic
x³ - 3x² + x + 1
the sum of the roots is 3 and the product of the roots is -1.
As the roots are a-b, a and a+b, the sum is then
(a-b) + a + (a+b) = 3
⇒ 3a = 3
⇒ a = 1.
The product of the roots is
(a-b)a(a+b) = -1
⇒ (1-b)(1+b) = -1
⇒ 1 - b² = -1
⇒ b² = 2
⇒ b = ±√2.
It follows that the three roots are
1, 1 - √2 and 1 + √2.
Hope this helps.
Answered by
1
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