 Hello and welcome to session. I am Bhuvika and we'll discuss with you fourth part of question 3 from exercise 5.1 Which is at page 89 of your book now the question says we have to find the ninth term of the given sequence First we will verify whether the sequence is having some pattern or not And if yes, that is if we will verify whether this is an arithmetic progression or not And if yes, just use the simple formula. So here the key idea is to verify The sequence is an AP and use a n is equal to a a n is equal to a plus n minus 1 into D as The formula to find the ninth term of the sequence. So this is the key idea. Just remember this A is the first term D is the common difference and n is the position of this term if you want to find 25th term of the sequence you simply substitute n as 25 and Proceed and plug in the values of a and a and simple calculations You'll get any number of terms using this formula, but the sequence must be in arithmetic progression So first we will verify whether the sequence is an AP or not. Let's proceed with the solution we have three by four five by four seven by four and Nine by four are the terms of the sequence. This is a one a two is five by four a Three is seven by four and a four is nine by four. So we will find common difference first Here a two minus a one is five by four minus three by four Which is two by four Similarly a three minus a two is seven by four minus five by four, which is two by four Similarly a four minus a three is also two by four hence The sequence is an AP and Common difference that is D is equal to two by four Now we have to find the ninth term We know that a n is equal to a plus n minus one into D Therefore a nine is equal to a plus eight D Where a is the first term and the first term was three by four and D is the common difference so a nine is nineteen by four after solving this hence the ninth term sequence is nineteen by four So that's all from this session. Just keep on revising the formulas. This formula is important Just keep on revising in until and unless you've got this formula in your blood veins so that's all keep practicing keep revising these questions and And very simple method no tricks nothing Implementation of formula direct implementation of formula. So that's all from this question. Have a nice time. Take care. Bye. Bye