Question

In an A.P if
D = 4 and is a³5= 123 find 'a'​

Answer 1

Answer:

sorry I don't know the answer

Step-by-step explanation:

sorry I don't know the answer

Answer 2

Given: Common difference of the AP is 4 and the 35th term is 123.

Need to find: The First term?

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As we know that,

The nth term of an AP is given by :

$\quad\quad\large\star\;\underline{\boxed{\sf{\pmb{a_n=a(n-1)\;d}}}}$

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where,

• an = nth term
• a = First term
• n = no. of term
• d = Common difference

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$\qquad\underline{\bf{\dag\;}\frak{Substituting\;the\;values\;in\;formula\;:}}$

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$:\implies\sf{123=a+(35-1)4}\\\\\\:\implies\sf{123=a+(34)4}\\\\\\:\implies\sf{123=a+136}\\\\\\:\implies\sf{123-136=a}\\\\\\:\implies\underline{\boxed{\frak{\pink{\pmb{a=-13}}}}}\;\bigstar$

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$\therefore\;{\underline{\textsf{Hence,\;the\;First\;term\;(a)\;of\;AP\;is\;{\textbf{-13}}}.}}$

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$\qquad\quad{\boxed{\underline{\mathbb{\bigstar{\pmb{\;\;MORE\;\;FORMULAS\;\;\bigstar}}}}}}$

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(1) Sum of n terms of an AP = $\sf{\pmb{S_n=\dfrac{n}{2}\bigg\lgroup 2a+(n-1)\;d\bigg\rgroup}}$

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(2) Sum of all terms of AP having Last term as ‘l’ = $\sf{\pmb{\dfrac{n}{2}\bigg\lgroup a+l\bigg\rgroup}}$⠀⠀⠀