1.solve each of the following equations.(express the answers as surds in their simplest form or in the form of a+bi if necessary, where a and b are real numbers.)
a)4x^2-12x-15=0
b)4x^2-12x+15=0
2.a)let k be a constant .express the discriminant of the quation x^2=7(x-k) in terms of k.
b) if the equations has no real roots, find the range of values of k.
math question 20p
2011-04-09 4:12 am
回答 (1)
2011-04-09 5:19 am
✔ 最佳答案
1(a) 4x^2 - 12x - 15 = 0x = [12 ± √(144 + 240)]/8
x = [12 ± √384]/8
x = [3 ± 2√6]/2
(b) 4x^2 - 12x + 15 = 0
x = [12 ± √(144 - 240)]/8
x = [12 ± √96i]/8
x = [3 ± √6i]/2
2(a) discriminant = 49 - 28k
(b) discriminant = 49 - 28k < 0 => k > 49/28 or k > 7/4
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