simply quadratic!!!!!

Algebra Level 2

If 2 and 3 are the roots of the polynomial 3x^2 - 2kx + 2m=0 then find the value of M


The answer is 9.

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4 solutions

Yash Singhal
Jul 20, 2014

By Vieta's formula, product of the roots is 2m/3 = 6 =6 which gives us m = 9 m=9 on cross-multiplication.

Since 2 2 and 3 3 are the roots, we have

( x 2 ) ( x 3 ) = 0 (x-2)(x-3)=0

x 2 3 x 2 x + 6 = 0 x^2-3x-2x+6=0

x 2 5 x + 6 = 0 x^2-5x+6=0

Multiplying it by 3 3 , gives

3 x 2 15 x + 18 = 0 3x^2-15x+18=0

So,

2 m = 18 2m=18

It follows that,

m = 9 \boxed{m=9}

If 2 , 3 2,3 are the roots then we can put x = 2 , 3 x=2,3 and the equation will be equal to 0 0 .We get 2 equations: 3 ( 2 ) 2 2 k ( 2 ) + 2 m = 0 ( a f t e r s i m p l i f i c a t i o n ) 2 k m = 6 \color{#3D99F6}{3(2)^2-2k(2)+2m=0\rightarrow(after\;simplification) 2k-m=6} 3 ( 3 ) 2 2 k ( 3 ) + 2 m = 0 ( a f t e r s i m p l i f i c a t i o n ) 6 k 2 m = 27 \color{#3D99F6}{3(3)^2-2k(3)+2m=0\rightarrow(after\;simplification) 6k-2m=27} m = 2 k 6 m=2k-6 .Substituting this into the second equation and simplifying,we get k = 7.5 k=7.5 .Substituting this into the first equation gives us m = 9 \boxed{m=9}

Kevin Patel
Jul 22, 2014

subtract both the equations to get the value of k=7.5...
then substitute 'k' in both equations to get M=9.

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