Q.

If a straight line having negative slope passing through the point P = (8, 2) meets the x-axis at A and y-axis at B respectively. Then the minimum value of OA + OB (O being origin) is _____

1 20  
2 18  
3 10  
4 15  

Ans.

(2)

Equation of line is y-2=m(x-8),   OA=8+2-m and OB=8(-m)+2

OA+OB=10+8(-m)+2-m≥18 (AM≥GM)