it is given that f(x)=x^2+kx and f(2)=10
a:find the value of k
b:hence find the value of a such that f(a)=a^2+9
唔識b help!!!
maths maths!
2008-12-28 6:51 am
回答 (2)
2008-12-28 6:54 am
✔ 最佳答案
(A)substitute x=2 into f(x)
2^2+2k=10
2k=6
k=3
(b)
f(x)=x^2+3x
f(a)=a^2+3a
Since a^2+3a=a^2+9
3a=9
a=3 !!!
2008-12-28 8:58 am
(a)Given: f(x)=x^2+kx and f(2)=10
Sol: f(x)=x^2+kx --------(1)
.......f(2)=10 --------------(2)
Sub (1) into (2),
f(2)=(2)^2+k(2)=10
....................2k =6
......................k=3 (The Answer)
(b)Given: f(a)=a^2+9
................f(a)=a^2+9=a^2+(3)(a)
.............................3a=9
...............................a=3
Sol: f(x)=x^2+kx --------(1)
.......f(2)=10 --------------(2)
Sub (1) into (2),
f(2)=(2)^2+k(2)=10
....................2k =6
......................k=3 (The Answer)
(b)Given: f(a)=a^2+9
................f(a)=a^2+9=a^2+(3)(a)
.............................3a=9
...............................a=3
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