Question

CW: If the 5th term and the 10th term of an arithmetic

Answer 1

Answer:

         a₂₁ = 188

Step-by-step explanation:

The n-th term of an arithmetic sequence:  $a_n=a_1+d(n-1)$

so:

    $a_5=a_1+d(5-1)\\a_5=a_1+4d\\a_1=a_5-4d\\a_1=44-4d\\\\a_{10}=a_1+d(10-1)\\ a_{10}=a_1+9d\\89=44-4d+9d\\45=5d\\d=9\\\\a_1=44-4\cdot9 = 8\\\\a_{21}=a_1+ 20d=8+20\cdot9=188$