(3x-5)(x+3)=(x+4)^2-28

Question

(3x-5)(x+3)=(x+4)^2-28

Answer 1

3x^2 + 9x - 5x - 15 = x^2  + 8x + 16 - 28
3x^2 + 4x - 15 = x^2 + 8x - 12
3x^2 - x^2 + 4x - 8x - 15 + 12 = 0 
2x^2 - 4x - 3 = 0 
D = 16 + 24 = 40
x1 = ( 4 + 2√10)/4 = (2 + √10)/2
x1 = ( 4 - 2√10)/4 = (2 - √10)/2