 Hello and welcome to the session. In this session we discuss the following question which says what must be subtracted from 2x square minus 7xy minus 3y square minus 1 to get 4x square minus 8xy minus 4y square plus 1. Let's move on to the solution. We have two algebraic expressions given to us 2x square minus 7xy minus 3y square minus 1 and 4x square minus 8xy minus 4y square plus 1. We need to find the algebraic expression which must be subtracted from this given algebraic expression to get this algebraic expression. For this we subtract this expression from the first algebraic expression given to us. So we first write the given expression 2x square minus 7xy minus 3y square minus 1. Now the expression to be subtracted would be written below this expression in such a way that the light terms occur one below the other. So 4x square would be written below 2x square then minus 8xy below minus 7xy minus 4y square below minus 3y square and plus 1 below minus 1. Next we need to subtract the second expression from the first expression. So we will change the sign of each term in the lower row from plus to minus or from minus to plus that is, now since the sign for this 4x square is plus we will say it would be minus now here it would be plus, here also it would be plus, here it would be minus. Now with these new signs of the terms of the lower row we would add column y's that is 2x square minus 4x square would give us minus 2x square then minus 7xy plus 8xy would give us plus xy then minus 3y square plus 4y square would give us plus y square minus 1 minus 1 would give us minus 2. So this is the required answer. So our final answer is minus 2x square plus xy plus y square minus 2 must be subtracted from 2x square minus 7xy minus 3y square minus 1 to get 4x square minus 8xy minus 4y square plus 1. So this is our final answer. This completes the session. Hope you have understood the solution for this question.