Add appropriate symbols and brackets to the following formula to make the equation hold. 1234 = 112345 = 1123456 = 11234567 = 1

Add appropriate symbols and brackets to the following formula to make the equation hold. 1234 = 112345 = 1123456 = 11234567 = 1

1×2+3-4=1
1-2+3+4-5=1
1+2+3-4+5-6=1
1×2+3+4+5-6-7=1