A.P is

_{The simplified A.P is √7, 2√7 3√7}

d= _{2√7 – √7 = √7 (2–1) = √7}

Next term of A.P means the fourth term = a₄

a₄ = a + (n–1) d

a₄= _{√7 + 3√7}

_{= 4√7}

_{= √112}