Question

Which term of the A.P 3,7,11,15,............will be 123 ? *​

Answer 1

$\huge\bf\boxed{\boxed{\underline{\purple{Answer!!}}}}$

$\huge\mathfrak\red{a = 3}$

$\huge\mathfrak\red{d = 7 - 3 = 4}$

$\huge\mathfrak\red{an = 123}$

$\huge\mathfrak\red{\:By \:using \:Formula }$

${\green{\overline{\green{\underline{\blue{\boxed{\orange{\mathtt{an = a + (n-1)d}}}}}}}}}$

➪ 123 = 3 + ( n - 1)4

➪ 123 - 3 = ( n - 1) 4

➪ 120 = ( n - 1 ) 4

➪ $\frac{120}{4}$ = (n - 1)

➪ $\cancel\frac{120}{4}$ = (n - 1)

➪ 30 = (n - 1)

➪ 30 + 1 = n

➪ 31 = n

$\huge\bf\boxed{\boxed{\underline{\red{n = 31}}}}$