Given '$$y$$' is a natural number, how many values of "$$y$$" are possible for $$(y^2 - 5y + 5)^{(y - 8)(y + 6)} = 1$$?
Expression : $$(y^2 - 5y + 5)^{(y - 8)(y + 6)} = 1$$
=> $$log(y^2 - 5y + 5)^{(y - 8)(y + 6)} = log(1)$$
=> $$(y-8)(y+6)log(y^2-5y+y)=0$$
Thus, either $$(y-8)=0$$ or $$(y+6)=0$$ or $$log(y^2-5y+5)=0$$
=> $$y=8,-6$$ ---------------(i)
or $$log(y^2-5y+5)=log(1)$$
=> $$y^2-5y+4=0$$
=> $$(y-4)(y-1)-0$$
=> $$y=4,1$$ -----------(ii)
Also, $$y^2-5y+5$$ can be equal to -1, and the power will be even; thus, it can be equal to 1.
$$y^2-5y+5$$ = -1
$$y^2-5y+6$$ = 0
y = 2 or 3
When y = 2, power will be(y-8)(y+6) = -48 even power, hence = 1
When y = 3, power will be 45 odd power, hence = -1
Thus, y = 2 also satisfies the condition.
From equations (i) and (ii), Possible values of $$y$$ (natural number) = 4
=> Ans - (A)
Create a FREE account and get: