The points A(0, 0), B(0, 4a - 5) and C(2a + 1, 2a +4) form a triangle. If angle ABC = 90, what is the area of triangle ABC? Choose the correct option.
A) 80	B) 75	C) 70	D) 60	E) 65
1/2bh=1/2(2a+1)(2a+4)   Now 4a-5=2a+4   2a=9   Therefore,   A(0,0); B(0,13); C(10,13)   1/2*10*13= 
<gadget id="calculator">1/2*10*13</gadget>
<output>65</output>
65   Answer: 65
<result>E</result>
The points A(0, 0), B(0, 4a - 5) and C(2a + 1, 2a +4) form a triangle. If angle ABC = 90, what is the area of triangle ABC?