好趕+超短的SUPER EASY,SILLY MATHS~

Q1) The line y=x-6 and the parabola y^2=8xintersect at A and B. Find the length
of AB
Sol
y^2=8x
(x－6)^2=8x
x^2－12x+36=8x
x^2－20x+36=0
(x－18)(x－2)=0
x=18 or x=2
(1) x=18
y=18－6=12
(2) x=2
y=2－6=－4
So
AB^2=(18－2)^2+(12+4)=512
AB=16√2

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