1.

For what value of n are the nth terms of aps:63,65,67......and3,10,17....equal?​

Answer»

\bf{\underline{Solution}}:-

\bf\dag{\underline\orange{{{For\:First\:AP}}}}

  • First term (a) = 63

  • Common difference (d) = 65 - 63 = 2

Now,

we KNOW that,

\orange{\bigstar}\:\:{\underline{\boxed{\bf\purple{a_n=a+(n-1)d}}}}

\rm\longrightarrow\:a_n=63+(n-1)\times{2}

\rm\longrightarrow\:a_n=63+2n-2

\rm\longrightarrow\:a_n=61+2n

\bf\dag{\underline\green{{{For\:second\:AP}}}}

  • First term (a) = 3

  • Common difference (d) = 10 - 3 = 7

Now,

we know that,

\blue{\bigstar}\:\:{\underline{\boxed{\bf\pink{a_n=a+(n-1)d}}}}

\rm\longrightarrow\:a_n=3+(n-1)\times{7}

\rm\longrightarrow\:a_n=3+7n-7

\rm\longrightarrow\:a_n=7n-4

Then,

According to the QUESTION,

\rm\:61+2n=7n-4

\rm\longrightarrow\:61+4=7n-2n

\rm\longrightarrow\:65=5n

\rm\longrightarrow\:\cancel\dfrac{65}{5}=n

\rm\longrightarrow\:13=n

\rm\longrightarrow\:n=13

Hence,13th term of these APs are equal.



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