Q:

Which equation has the solutions mc013-1.jpg? 3x2 – 5x + 7 = 0 3x2 – 5x – 1 = 0 3x2 – 10x + 6 = 0 3x2 – 10x – 1 = 0

Accepted Solution

A:
Given\:solutions:[tex]\frac{5+2\sqrt{7}}{3}\:and\:\frac{5-2\sqrt{7}}{3}[/tex].Therefore, factors of the equation would be [tex](x-\frac{5+2\sqrt{7}}{3})\:and\:(x-\frac{5-2\sqrt{7}}{3})[/tex]Let us multiply those two factors to get the equation, we get [tex]\left(x-\frac{5+2\sqrt{7}}{3}\right)\left(x-\frac{5-2\sqrt{7}}{3}\right)[/tex][tex]\mathrm{Apply\:FOIL\:method}:\quad \left(a+b\right)\left(c+d\right)=ac+ad+bc+bd[/tex][tex]a=x,\:b=-\frac{5+2\sqrt{7}}{3},\:c=x,\:d=-\frac{5-2\sqrt{7}}{3}[/tex][tex]=xx+x\left(-\frac{5-2\sqrt{7}}{3}\right)+\left(-\frac{5+2\sqrt{7}}{3}\right)x+\left(-\frac{5+2\sqrt{7}}{3}\right)\left(-\frac{5-2\sqrt{7}}{3}\right)[/tex][tex]=xx-\frac{5-2\sqrt{7}}{3}x-\frac{5+2\sqrt{7}}{3}x+\frac{5+2\sqrt{7}}{3}\cdot \frac{5-2\sqrt{7}}{3}[/tex][tex]=x^2-\frac{5x-2\sqrt{7}x}{3}-\frac{5x+2\sqrt{7}x}{3}-\frac{1}{3}[/tex][tex]\mathrm{Combine\:the\:fractions\:}-\frac{5x-2\sqrt{7}x}{3}-\frac{5x+2\sqrt{7}x}{3}-\frac{1}{3}:\quad \frac{-\left(5x-2\sqrt{7}x\right)-\left(5x+2\sqrt{7}x\right)-1}{3}[/tex][tex]=x^2+\frac{-\left(5x-2\sqrt{7}x\right)-\left(5x+2\sqrt{7}x\right)-1}{3}[/tex][tex]\mathrm{Expand}\:-\left(5x-2\sqrt{7}x\right)-\left(5x+2\sqrt{7}x\right)-1:\quad -10x-1[/tex][tex]=x^2+\frac{-10x-1}{3}[/tex]Setting it equal to 0.[tex]x^2+\frac{-10x-1}{3}=0[/tex]Multiplying whole equation by 3, we get [tex]3x^2-10x-1 = 0[/tex]Therefore, correct option is D [tex]3x^2-10x-1 = 0[/tex]