I’m not sure about these two problems... PLEASE HELP

Q1: a_n=2n+3Q2: The 12th term of sequence is 70Step-by-step explanation:Question No. 1Given sequence is: 5,3,1,-1,-3....Common difference is the difference between consecutive terms of an arithmetic sequence.We have to find the common difference first[tex]d=a_2-a_1=5-3=2\\a_3-a_2=3-1=2[/tex]The first term is: 5The general formula for arithmetic sequence is:[tex]a_n=a_1+(n-1)d[/tex]Putting the values of a1 and d[tex]a_n=5+(n-1)(2)\\a_n=5+2n-2\\a_n=2n+3[/tex]Question No. 2:Given[tex]a_7=40\\a_18=106[/tex]According to general formula, the expression for 7th and 18th term is:[tex]a_7=a_1+(7-1)d=>40=a_1+6d\ \ \ \ Eqn\ 1\\a_18=a_1+(18-1)d = >106=a_1+17d\ \ \ \ Eqn\ 2\\Subtracting\ Eqn\ 1\ from\ eqn\ 2\\a_1+17d-a_1-6d=106-40\\11d=66\\Dividing\ both\ sides\ by\ 11\\\frac{11d}{11}=\frac{66}{11}\\d=6\\Putting\ d=6\ in\ eqn\ 1\\40=a_1+6(6)\\40=a_1+36\\a_1=40-36\\a_1=4[/tex]Putting the values of a1 and d in general form[tex]a_n= a_1+(n-1)(6)\\a_n=4+6n-6\\a_n=6n-2\\Putting\ n=12\ \\a_{12}=6(12)-2\\=72-2\\=70[/tex]The 12th term is 70Answers: Q1: a_n=2n+3Q2: The 12th term of sequence is 70Keywords: Arithmetic sequence, Common DifferenceLearn more about arithmetic sequence at:brainly.com/question/4980053brainly.com/question/5002251#LearnwithBrainly