Question

favor me envie o calculo
( x - 9 )² = x² - 40  

Answer 1

$(x-9)^{2} = x^{2} -40 \\ \\ \\ (x-9)*(x-9)= x^{2} -40 \\ \\ x^{2} -9x-9x+81= x^{2} -40 \\ \\ x^{2} -18x+81- x^{2} +40=0 \\ \\ -18x+121=0 \\ \\ -18x=-121 \\ \\ x= \frac{-121}{-18} \\ \\ x=6,72...$

Answer 2

$(x - 9)^2 = x^2 - 40 \\ \\ \\ x^{2} -18x +81 = x^{2} - 40 \\ \\ x^{2} -18x +81 - x^{2} + 40 =0 \\ \\ -18x + 121 = 0 \\ \\ - 18x + 121 *(-1) \\ \\ 18x -121 = 0 \\ \\ 18x = 121 \\ \\ x= \frac{121}{18}$