easy one but i am not getting any of options

\begin{vmatrix} 3x &4x &-5 \\ 2x^{2}&9 &2x \\ x& 8 & 3x \end{vmatrix}=ax^{4}+ bx^{3}+cx^{2}+ dx+e,then,
the value of 6a+5b+4c+3d+2e is equal to.......
a.273 b.235 c.-15 d.-53

10 Answers

1
rahul nair ·

plsss. reply soon , i m just not getting my mistake.......

1
Akand ·

me gettin -157........might be calcuilation mistake......

1
Optimus Prime ·

3x(27x-16x)-4x(6x3-2x2)-5(16x2-9x)
=33x2-24x4+8x3+45x
=-24x4+8x3-47x2+45x

comparing we have a=-24
b=8
c=-47
d=45
e=0

6a= -144
5b=40
4c=-188
3d=135
2e=0

adding all we get -157 so either ur options are wrong or the question typed is wrong

1
Optimus Prime ·

option c shud be -157

1
rahul nair ·

ya...... amit even i m getting -157........

1
Optimus Prime ·

that means we are rite rahul

1
Akand ·

ya sorry typo..........mine is also -157.........

62
Lokesh Verma ·

There is a much simpler method by derivatives...

can you guys see it?!

1
Akand ·

but bhaiyya wont tht be too big.....i men three determinants and differntiaion ................so wont just opening be better?????

21
tapanmast Vora ·

No AKand, not at all
it wud be real short,

put x=0; get e
take deriv. put x=0, get d

divide by x^4 on both sides put x --> ∞ get a

similarly get b,c

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