3 equations and the area of a triangle

Geometry Level pending

Let x x , y y , and z z be real numbers such that: x + 2 y z + 1 = 0 |x+2y| - |z+1| = 0 , 2 2 x z = 1 6 y + 7 2^{2x-z} = 16^{y+7} and 4 x 2 5 y + 7 z = 1700 4x^2 - 5y + 7z = 1700 . Let the sum of all possible values for ( x + y + z ) (x+y+z) , such that in any ( x + y + z ) (x+y+z) , x x , y y , and z z all satisfy the equations above, be k k . Determine the area of an equiangular triangle with side length k k . Round your answer to 2 2 decimal places. A scientific calculator is allowed.

35.172 200.63 197.52 21.358 228.08 37.89

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

Yashas Ravi
Mar 16, 2018

Solve the triple-system of equations. By simplification, x + 2 y = z + 1 x+2y=z+1 , x + 2 y = z 1 x+2y=-z-1 , 2 x z = 4 y + 28 2x-z=4y+28 , and 4 x 2 5 y + 7 z = 1700 4x^2-5y+7z=1700 . The 2 2 possible expressions for x x and z z resulted in the fact that an equation with an absolute value in both sides will split into 2 2 equations (the 1 1 st and 2 2 nd equation, shown above). The third equation resulted in from the equation 2 2 x z = 1 6 y + 7 2^{2x-z} = 16^{y+7} , where 2 x z = 4 ( y + 7 ) = 4 y + 28 2x-z=4(y+7) = 4y+28 . I multiplied by 4 4 because of the fact that 16 = 2 4 16=2^4 . The 4 4 th equation (the quadratic) is given in the problem.

A good variable to solve for, in my opinion (you could solve for any) is y y : In terms of y y , x = 27 + 6 y x=27+6y (where z = 8 y + 26 z=8y+26 ), and x = 2 y 3 + 9 x= \frac{2y}{3}\ +9 (where z = 10 z=-10 - 8 y 3 \frac{8y}{3} ).

You should get 4 4 possible values for ( x + y + z ) (x+y+z) : 23.484 -23.484 , 35.172 35.172 , 35.165 35.165 , and 25.495 -25.495 . Then, Sum all of the values to get 21.358 21.358 . Since the area of an equiangular, or equilateral triangle is ( s 2 0.25 3 ) (s^2 * 0.25\sqrt{3}) , where s = k = 21.358 s=k=21.358 , the area is 197.52 197.52 units 2 ^2 .

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...