If a1= 9 and an = 5a(n-1) +1 then find the value of a4

How can (square root of 25) ^2 be rewritten?

Aline is perpendicular to another line m2= (-1/m1), where m1 is the slope of the original line and m2 is the slope of the perpendicular line. which of the following equations represents the line that passes through the point (-2,1) and is perpendicular to the line below?

Which of these figures must be a rectangle?