(a)Find the range of values of x for which x(10-x)≥24.
(b)Find the value of k for which 2y+x=k is a tangent to the curve y²+4x=20.
a-maths!!!!!!
2007-12-18 5:38 am
回答 (2)
2007-12-18 6:25 am
✔ 最佳答案
As follows:圖片參考：http://i238.photobucket.com/albums/ff245/chocolate328154/Maths047.jpg?t=1197901523
參考: My Maths Knowledge
2007-12-18 7:20 am
x(10-x)≧24
10x-x²≧24
x²-10x+24≦0
(x-4)(x-6)≦0
4≦x≦6
2y+x=k
put x=k-2y into
y²+4(k-2y)=20
y²-8y+4k-20=0
Δ=(-8)²-4(1)(4k-20)=0
64-16k+80=0
-16k=-144
k=9
10x-x²≧24
x²-10x+24≦0
(x-4)(x-6)≦0
4≦x≦6
2y+x=k
put x=k-2y into
y²+4(k-2y)=20
y²-8y+4k-20=0
Δ=(-8)²-4(1)(4k-20)=0
64-16k+80=0
-16k=-144
k=9
參考: me
收錄日期: 2021-04-23 20:47:06
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