If g(x)=3x+2 and 2g2(x)−g(x2)−5g(x)=7 are satisfied by x1 and x2, then the value of x1+x2 is ...
Explanation
Given the function g(x)=3x+2. We will substitute this function into the given equation.
2g2(x)−g(x2)−5g(x)−7=0
First, determine the forms of g2(x) and g(x2):
g2(x)=(3x+2)2=9x2+12x+4
g(x2)=3(x2)+2=3x2+2
Substitute these forms into the initial equation:
2(9x2+12x+4)−(3x2+2)−5(3x+2)−7=0
(18x2+24x+8)−(3x2+2)−(15x+10)−7=0
Group like terms:
(18−3)x2+(24−15)x+(8−2−10−7)=0
15x2+9x−11=0
This quadratic equation has roots x1 and x2. The sum of the roots of a quadratic equation ax2+bx+c=0 is x1+x2=−ab.
x1+x2=−159
x1+x2=−53
Thus, the value of x1+x2 is −53.