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irina1246 [14]
3 years ago
12

Which is the polynomial function of lowest degree with rational real coefficients, a leading coefficient of 3 and roots StartRoo

t 5 EndRoot and 2?
a) f (x) = 3 x cubed minus 6 x squared minus 15 x + 30
b) f (x) = x cubed minus 2 x squared minus 5 x + 10
c) f (x) = 3 x squared minus 21 x + 30
d) f (x) = x squared minus 7 x + 10
Mathematics
2 answers:
weqwewe [10]3 years ago
7 0

Answer:

its a

Step-by-step explanation:

anastassius [24]3 years ago
4 0

Answer:

a) f(x)=3x^{3}-6x^{2}-15x+30

Step-by-step explanation:

1) In this question we've been given "a", the leading coefficient. and two roots:

x_{1}=\sqrt{5}\:x_{2}=2

2) There's a theorem, called the Irrational Theorem Root that states:

If one root is in this form x'=\sqrt{a}+b  then its conjugate x''=\sqrt{a}-b. is also a root of this polynomial.

Therefore

x_3=-\sqrt{5}

3) So, applying this Theorem we can rewrite the equation, by factoring. Remembering that x is the root. Since the question wants it in this expanded form then:

f(x)=3(x-\sqrt{5})(x+\sqrt{5})(x-2)\Rightarrow 3x^{3}-6x^{2}-15x+30

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