The points A(0, 0), B(0, 4a - 5) and C(2a + 1, 2a + 5) form a triangle. If angle ABC = 90, what is the area of triangle ABC?	Choose one:
A) 80 B) 82.5 C) 78.5 D) 75.5 E) 74
1/2bh=1/2(2a+1)(2a+5)   Now 4a-5=2a+5   2a=10 ,a=5   Therefore,   A(0,0); 82.5(0,15); C(10,15)   1/2*11*15= 
<gadget id="calculator">1/2*11*15</gadget>
<output>165/2 = around 82.5</output>
82.5   Answer: 82.5
<result>B</result>
The points A(0, 0), B(0, 4a - 5) and C(2a + 1, 2a + 5) form a triangle. If angle ABC = 90, what is the area of triangle ABC?