4/x = x /4
⇒2 * 2x * 4/x = 2 * 2x * x/4
⇒2*2 *x*4/x = 2 * 2x * 4/x
⇒2 * 2 * 4 =2 * 2 x * 4/x
⇒16 = 2 * 2 x * 4/x
⇒16 = 4 x * 4/x
⇒ 16 = x x
⇒16 = x²
⇒16 - x² = 0
⇒- x² + 16 = 0
⇒ -1 ( x²-16 ) =0
⇒−1(x²+4x−4x−16)=0
⇒−1((x²+4x)+(−4x−16))=0
⇒−1(x(x+4)−4(x+4))=0
⇒−1(x−4)(x+4)=0
⇒x-4 = 0 x + 4 = 0
⇒x = 4 x = -4
