1.

find the polynomial whose double of zeros of x square minus x minus 6

Answer»
x²-x-6 can be written as
x²+2x-3x-6which can be written as
2(x+2) -3(x+2) or (x+2)(x-3)
then roots are -2 and 3. then polynomial whose roots are -4 and 6 is
x²- (-4+6)x +(-4)(6) = x² -2x -24.

Alternatively

we know that root1+root2= -b/a -----(i)
and root1×root2= c/a -------(ii)

then, let the roots of new polynomial be (2A) and (2B), where A and B are roots of x²-x-6 ---------(iii).
then new polynomial can be written as
x² -(Sum of roots)x + product of roots
x² - (2A+2B)x +(2A)(2B) which is
x²- 2x(A+B) +4AB -----(iv)

from (i),(ii),(iii) A+B =1 and AB= -6
putting in (iv),
x² - 2x - 24


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