Question

X squared minus x equals 72

Answer 1

`x^2-x=72\\ x^2-x-72=0\\ x^2-9x+8x-72=0\\ x(x-9)+8(x-9)=0\\ (x+8)(x-9)=0\\ x=-8 \vee x=9`

Answer 2

`x^2-x=72\\\\x^2-x-72=0\\\\a=1;\ b=-1;\ c=-72\\\\\Delta=b^2-4ac\to\Delta=(-1)^2-4(1)(-72)=1+288=289\\\\x=(-b\pm\sqrt\Delta)/(2a)\\\\\sqrt\Delta=√(289)=17\\\\x=(-(-1)\pm17)/(2(1))=(1\pm17)/(2)\Rightarrow x=(-16)/(2)=-8\ or\ x=(18)/(2)=9`