4x²-17x-42 by factor
4x²-17x-42=4(x²-17/4x)-42=4[x²-17/4 x+(-17/8)²-(-17/8)²]-42=4(x-17/8)²-289/64-42=4(x-17/8)²-(289+2688)/64=4(x-17/8)²-2974/64=[(2x-34/8)²-(√2974/8)²]=(2x-34/8 +(√2974/8))(2x-34/8-(√2974/8)=[2x+(√2974-34)/8][2x-(√2974+34)/8]
