Question

(i) किसी समांतर श्रेढ़ी का 8वाँ पद -23 तथा 12वाँ पद -39 है तो a? d?
​

Answer 1

given terms.↼

➝ $\sf\</strong><strong>g</strong><strong>r</strong><strong>e</strong><strong>e</strong><strong>n</strong><strong>{</strong><strong>a</strong><strong>8</strong><strong> </strong><strong>=</strong><strong> </strong><strong>a</strong><strong> </strong><strong>+</strong><strong> </strong><strong>7</strong><strong>d</strong><strong> </strong><strong>=</strong><strong> </strong><strong>-</strong><strong>2</strong><strong>3</strong><strong>}$

➝$\sf\</strong><strong>g</strong><strong>r</strong><strong>e</strong><strong>e</strong><strong>n</strong><strong>{</strong><strong>a</strong><strong>1</strong><strong>2</strong><strong> </strong><strong>=</strong><strong> </strong><strong>a</strong><strong>+</strong><strong> </strong><strong>1</strong><strong>1</strong><strong>d</strong><strong> </strong><strong>=</strong><strong> </strong><strong>-</strong><strong>3</strong><strong>9</strong><strong>}$

$\huge\sf\underline{\underline{\</strong><strong>g</strong><strong>r</strong><strong>e</strong><strong>e</strong><strong>n</strong><strong>{</strong><strong>solu</strong><strong>tion</strong><strong>}}}$

✧$\sf\</strong><strong>g</strong><strong>r</strong><strong>e</strong><strong>e</strong><strong>n</strong><strong>{</strong><strong>a</strong><strong> </strong><strong>+</strong><strong> </strong><strong>7</strong><strong>d</strong><strong> </strong><strong>=</strong><strong> </strong><strong>-</strong><strong>2</strong><strong>3</strong><strong>}$( i )

$\sf\green{a + 11d = -39}$( ii )

☆substracting equation frist and second

WE GET,

• $\sf\green{a + 7d = -23}$
• $\sf\green{a + 11d = -39}$

_________________

• $\sf\green{4d = -16}$
• $\sf\green{d = -4}$

*IF"d ' = -4 than putting value of d in equation first we get,

• $\sf\green{a+7d = -23}$
• $\sf\green{a + (7×-4)= -23}$
• $\sf\green{a - 28 = -23}$
• $\sf\green{a = -23 + 28}$
• $\sf\green{ a = 5}$

$\huge\sf\underline{\underline{\red{AnsWeR}}}$

☞ $\sf\green{</strong><strong>a</strong><strong> = </strong><strong>5</strong><strong>}$

☞ $\sf\green{d = -</strong><strong>4</strong><strong>}$