AS maths! need help please!?

🎓 學業台家課輔助

Amy

2009-11-23 9:51 pm

f(x)=4x^2+12x+9

a) determine the number of real roots that exist for the equation f(x)=0

b) Solve the equation f(x)=8

show methods please :)

回答 (2)

[匿名]

2009-11-24 8:24 am

✔ 最佳答案

ax^2+bx+c=0

a)If the determinant, b^-4ac=0 there is only one root.
12^2-(4*4*9)=0 so one root
(2x+3)(2x+3)
x=-3/2

b)(4 *(8^2))+(12*8)+9
=361

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[匿名]

2009-11-24 5:56 am

First factor.
(2x + 3)(2x +3) = 0
2x +3 = 0
2x = -3
x = -3/2

F(8) = 4(8)^2 + 12(8) + 9
f(8) = 256 + 96 + 9
f(8) = 361

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