The quadratic trinomial can be factor using the following formula:
[tex] ax^2+bx+c=a(x-x_1)(x-x_2), \text{ where } x_1,\ x_2 \text{ are trinomial roots} [/tex].
1. For the quadratic trinomial [tex] x^2 + 3x - 4 [/tex] find the roots:
[tex] D=3^2-4\cdot (-4)=9+16=25,\ \sqrt{D}=\sqrt{25} =5,\\
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x_1= \dfrac{-3-5}{2} =-\dfrac{8}{2}=-4,\ x_2=\dfrac{-3+5}{2} =\dfrac{2}{2}=1 [/tex].
2. The factoring form of trinomial is
[tex] x^2+3x-4=(x+4)(x-1) [/tex].
3. The factors are x+4 and x-1
Answer: correct choice is C.
