Problem
COM-B1-M06-P011 Changing Three Signs?
#11
★★☆☆☆ Level 2 of 5
There are \(6\) plus signs on the board. In one move, exactly \(4\) signs may be changed. Can exactly one minus be obtained?
The product of signs is preserved.
Changing \(4\) signs multiplies the product by \((-1)^4=1\). Initially the product is \(+1\), while with one minus it is \(-1\). Impossible.
Similar task with a different number of changed signs.