Latest TCS Aptitude Question SOLUTION: Let a be a real number such that a3 - 3a2 + 27 = 0. Then the value of a7 + 486a2 is 738 2187 0 -2187

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Let a be a real number such that a3 - 3a2 + 27 = 0. Then the value of a7 + 486a2 is

738
2187
0
-2187

Asked In TCS NITISH KUMAR (10 years ago)

Unsolved Read Solution (3)

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Read Solution (3) :

Tanu  (10 years ago)

2187 is the answer.
Just multiply the above equation by a^4
we get, a7-3a6+27a4=0
a7=3a6-27a4--------equation 1

Now to find a6 multiply above equation by a^3
we get, a6-3a5+27a3=0
a6=3a5-27a3--------equation 2

To find a6 multiply above equation by a^2
we get, a5-3a4+27a2=0
a5=3a4+27a2--------equation 3

Now a7=3a6-27a4 from equation 1
=3(3a5-27a3)-27a4 from equation 2
=9a5-81a3-27a4
=9(3a4-27a2)-81a3-27a4 from equation 3
=27a4-243a2-81a3-27a4
=-243a2-81a3
=-243a2-81(3a2 -27) from the given equation
a7 =-243a2-243a2+2187
a7 =-486a2+2187

So, a7 + 486a2 = 2187

Is this solution Helpfull? Yes (59) | No (2)  

Guru Pranav  (10 years ago)

It means break it until and unless you don't come to the power of two. :)

Is this solution Helpfull? Yes | No   

Payal Parul  (10 years ago)

2000+187aise ho hoga

Is this solution Helpfull? Yes | No   

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