設(shè)A(a,0),B(b,0),a,b為2x² - 4x -1 = 0的兩個根(b> a)
a+b = -(-4)/2 = 2,ab = -1/2
(1)
AB = b - a = √(b-a)² = √[(a+b)² - 4ab] = √[2² - 4(-1/2)] = √6
(2)
x = 0,y = -1,OC = 1
△ABC面積 = (1/2)*AB*OC = (1/2)√6*1 = √6/2
(3)
2x² - 4x -1 = 0
x = (2±√6)/2
A((2-√6)/2,0),B((2+√6)/2,0)
y = 2x² - 4x -1 = 2(x - 1)²- 3
P(1,3)
設(shè)對稱軸與軸交于D,D(1,0)
四邊形ABPC面積 = △AOC面積 + 梯形OCPD面積 + △BPD面積
= (1/2)OA*OC + (1/2)(OC+DP)*OD + (1/2)*DB*DP
= (1/2)[(√6 - 2)/2]*1 + (1/2)(1 + 3)*1 + (1/2)[(2+√6)/2 - 1]*3
= √6 + 3/2