Answer :
suppose the length needed to cut off as x
set quadratic equations and use the pythagorean identity (21-x)^2+(42-X) ^2=(45-x)^2
expand and distribute both sides to get quadratic equation x^2-36x+180=0, and find x to be 6cm
set quadratic equations and use the pythagorean identity (21-x)^2+(42-X) ^2=(45-x)^2
expand and distribute both sides to get quadratic equation x^2-36x+180=0, and find x to be 6cm