Dancers all over

Algebra Level 2

There are 3 dancers, Bingo , Mingo \color{#D61F06}{\text{Bingo}} ,\color{#3D99F6}{\text{Mingo}} and Tingo \color{#20A900}{\text{Tingo}} .

They are dancing, and during their dance, they move along the path in the Cartesian plane as stated below.

Bingo : : : : y = x 3 52 x + 96 \color{#D61F06}{\text{Bingo}} :::: \color{#D61F06}{y =x^3-52x+96 }

Mingo : : : : y = x + 44 \color{#3D99F6}{\text{Mingo}} :::: \color{#3D99F6}{y= x+44}

Tingo : : : : y = x 4 24 x 3 + 148 x 2 336 x + 256 \color{#20A900}{\text{Tingo}} :::: \color{#20A900}{y =x^4 - 24x^3 + 148x^2 - 336x + 256}

They all yell out "WOW" if they all meet at a point.

The point where they yell "WOW" can be stated as ( a , b ) (a,b) in Cartesian system, and a a and b b are integers . Find the value of a + b \color{#69047E}{a+b}


The answer is 46.

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2 solutions

Aditya Raut
Jun 16, 2014

In B i n g o \color{#D61F06}{Bingo} 's equation, put the value of y y from M i n g o \color{#3D99F6}{Mingo} 's equation. Then you get the equation

x + 44 = x 3 52 x + 96 x+44 = x^3 -52x+96

That is , x 3 53 x + 52 = 0 x^3-53x + 52=0

By observation only, 1 1 is a root of this equation, thus 1 is a common solution of B i n g o \color{#D61F06}{Bingo} and M i n g o \color{#3D99F6}{Mingo} 's equations for the point of yelling.

And the equations actually are

B i n g o : : : : y = ( x 2 ) ( x 6 ) ( x + 8 ) \color{#D61F06}{Bingo} :::: \color{#D61F06}{y= (x-2)(x-6)(x+8)}

M i n g o : : : : y = x + 44 \color{#3D99F6}{Mingo} :::: \color{#3D99F6}{ y= x+44}

T i n g o : : : : y = ( x 16 ) ( x 4 ) ( x 2 ) 2 \color{#20A900}{Tingo} :::: \color{#20A900}{y = (x-16) (x-4) (x-2)^2}

Even if you can't factorize, just try putting x = 1 x=1 in all equations, everytime you get the value of y y as 45 45 .

Hence the point where they meet is ( 1 , 45 ) (1,45) and hence asked a n s w e r \color{#69047E}{answer} is 46 \color{#69047E}{\Huge{\boxed{46}}}

Cody Johnson
Jun 16, 2014

Intersecting Bingo and Mingo, we have x 3 52 x + 96 = x + 44 x = 1 , 1 ± 209 2 x^3-52x+96=x+44\implies x=1,\frac{-1\pm\sqrt{209}}{2} . Hence, x = 1 x=1 because the coordinates must be integers. All that is left is to check that y = 45 y=45 in all cases, which it does.

Why does that imply x=1?

Sithija Abhishek - 5 years, 3 months ago

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