public static double[][] subtract(double A[][], double B[][]){
		if(A.length != B.length || A[0].length != B[0].length)
			return null;
		double T[][] = new double[A.length][A[0].length];
		for(int i = 0; i<T.length; i++){
			for(int j = 0; j<T[0].length; j++){
				T[i][j] = A[i][j]-B[i][j];
			}
		}
		return T;
	} //end subtract method