F.6 Maths

Question

1) If the circumference of a circle is increased by 40%, then the area of the circle is increased by
ans.:96%

2) If z varies directly as x and inversely as y^2, which of the following must be constant?
ans.:x/(y^2)(z)
答案唔係應該分子分母調轉的嗎?

3) The coordinates of the points A and B are (1,-3) and (-5,7) respectively. If P is a point lying on the straight line y=x+2 such that AP=PB, then the coordinates of P are
ans.:(3,5)

4) Let O be the origin. If the coordinates of the points A and B are (18,-24) and (18,24) respectively, then the x-coordinates of the orthocentre of triangle OAB is
ans.:-14

不明白為何會是這個答案,請各位詳細列個步驟俾我呀,thz!>,<"

? · Accepted Answer

1 The circumference of a circle is increased by 40%  => radius increase 40%So, area increase 1.4 * 1.4 - 1 = 96%2 z = Kx/y^2 where K is a constant=> x/y^2z = 1/K is a constantLet P(a,a + 2)(a - 1)^2 + (a + 5)^2 = (a + 5)^2 + (a - 5)^2(a - 1)^2 = (a - 5)^2a - 1 = -(a - 5)a = 3, so P(3,5)4 Slope of OA = 24/18 = 4/3Let the orthocentre P(x,0)Line BP: (y + 24) = (-3/4)(x - 18)Sub. y = 0, x = 14 and P(14,0)

F.6 Maths

1 個解答