F4數學

一l神l一

It is given that g(x)=ax^2+bx+4,g(1)=1 and g(2)=2
a.find the values of a and b
b Is it true that g(3)=3?Explain your answer
幫手解答~~~~

[ 本帖最後由 一l神l一 於 10-1-3 05:27 PM 編輯 ]

終極堂打雜

It is given that g(x)=ax^2+bx+4,g(1)=1 and g(2)=2
a).find the values of a and b
1 = a+b+4
2 = 4a+2b+4
a = 2
b = -5

b) Is it true that g(3)=3?Explain your answer
g(3) = 2(9)-5(3)+4 = 8 =/= 3

kingtom

樓上跳哂steps...我補補~
It is given that g(x)=ax^2+bx+4,g(1)=1 and g(2)=2
a.find the values of a and b
b.Is it true that g(3)=3?Explain your answer.

a.
g(1) = a+b+4 = 1---(1)
g(2) = 4a+2b+4 = 2---(2)
*Solve the simultaneous equation (1) and (2)*
(1)x4 = 4a+4b+16 = 4---(3)
(3)-(2),
2b+12=2
b=-5
Put b=-5 into (1),
a+(-5)+4 = 1
a = 2