Calculation: keUfrE - 1

x1* x2* y1* y2 =
0

x1* x2* y1* y2 = 0 $x1\cdot x2\cdot y1\cdot y2$ = 0

x1* x2* y1* y2 = 0 $x1\cdot x2\cdot y1\cdot y2$ = 0

x1* x2* y1* y2 = 0 $x1\cdot x2\cdot y1\cdot y2$ = 0

x1 =

0

/ x2/ y1/ y2

$x1$ = $\frac{0}{x2\cdot y1\cdot y2}$

x1 = 0 $x1$ = 0