Q9 of 64 Page 49

2 + √3 and 2 — √3 are the zeros of p(x) = x4 — 6x3 — 26x2 + 138x — 35. Find the remaining zeros of p(x).

Given, 2 + √3 and 2–√3 are zeros of p(x).


and are the factors of p(x).


Thus = (x2 – 4x + 4 –3) = (x2 – 4x + 1) is also a factor of p(x).


To find the remaining zeros, we find the remaining factors using the division process.


Here, dividend polynomial = p(x) = 2x4 + 7x3 — 8x2 — 14x + 8


and divisor polynomial = s(x) = x2 – 2



p(x) = 2x4 + 7x3 — 8x2 — 14x + 8 = (x2 – 4x + 1)(x2 – 2x — 35)


On factorising x2 – 2x — 35, we get


x2 – 2x — 35 = x2 –7x + 5x— 35


= x (x – 7) + 5 (x – 7)


= (x – 7) (x + 5)


Hence the other two zeros of p(x) are 7 and –5.


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