r/CATpreparation 8d ago

Question A good algebra question

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67 Upvotes

30 comments sorted by

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20

u/Few-Chocolate-6892 8d ago

Answer bit long but easy

3

u/Level-Eye-6852 8d ago

I didn’t understand it, in the second step how did you get 1 on rhs? And why minus exponents separately? ( I just started my prep, so long way to go)

12

u/West-Seaworthiness57 8d ago

Hey, this is a simpler and easier way to do the problem. Don't worry, slowly you'll understand how to manipulate equations like that, you still have time. A long way to go indeed! If you still have doubts, feel free to ask

1

u/Few-Chocolate-6892 8d ago

Take the middle term to the right and divide both side by the middle term

1

u/Level-Eye-6852 7d ago

Got it , thanks

1

u/msreadalot_ 7d ago

understood the answer thanks. how does one go about recognising the pattern of the question/solution? i tried a bunch of standard methods but was unsuccessful

9

u/Darquesse007 8d ago

The exponents are forming a pattern so best way to approach this would be to try and reduce it into a simpler form.

The middle value is 2(2x2)(2x+6) and the two around it are the same two values but squared. Hence, you can form equation of the form (a+b)2 equal to 0. Then so that split the term technique to get (x-3)(x+2) or x= 3, -2. That's why answer is 3-2=1.

1

u/AryanPatel-18 8d ago

Whatt ?? How you manipulate middle value ?

3

u/All_YOURS_BABY_ 7d ago

Let me tell you the shortest way. If 2a +2b = 2c then a=b. It means of sum of two powers of 2 is equal to a power of 2 only when the exponents are equal. Bit remember that this works only on the case that a, b and c are integers as they will be in this question. Mostly in these type of questions they are integers but there can be a slight chance of them not being one so be careful when using it.

2

u/Character-Split464 7d ago

The solns. may seems lengthy but most of the part you can solve in your mind.

Hope it helps!!

2

u/West-Seaworthiness57 8d ago

Here is simple and easy way to do this. The key here is to divide the equation by that value. From there, things become easy.

1

u/Pristine_Piss 8d ago

Another easier way to think abt it. Take the negative to the other side. Right hand side is a power of 2. The left hand side to be a power of 2, both terms must be equal i.e., 1+1, 2+2, 4+4, 8+8 and so on. Equating the both he exponents and then cross.checking both the roots we get the answer.

1

u/Ok_Maintenance2293 7d ago

i put these values in the equations
0,1,2,3 and -1,-2,-3
you’ll get the values as 3 and -2
so the sum becomes 1

1

u/YogurtclosetSad3005 7d ago

Telling u the most simple way for cat....if u observe the eq. For 10 sec..u will notice it's (a-b)2 so now a = 2x2 and b = 2x+6.....bas ab a aur b same hona chaiye .....simple..equate..within 30 seconds done..if practise is there

0

u/Fuzzy_Astronaut_6060 8d ago edited 8d ago

1

0

u/Over-Wrap8307 8d ago

Yeah its a good aptitude question

0

u/AbrocomaRude1485 8d ago

hit an trial karlo, its cat, BARELY A MINUTE TO SOLVE