4 x 4 x 4 = 64 is the answer
Your answer is the matrix with the top row of -8 20 0 and bottom row of
4 32 -4
All triangles interior angles equal 180
So these 3 angles = 180
(5x+1)² = 7; expand: 25x² + 10x +1 = 7 or 25x² + 10x -6 = 0
Solve this quadratic for x:
x = [-b + √(b² - 4ac)]/2a and x = [-b - √(b² - 4ac)]/2a
Plug the values and you'll find :
x = (- √7 - 1)/5 (answer C)
x = (+√7 -1)/5 (answer E)
