Q. The function f is defined by f(x)=ax2+bx+c, where a,b, and c are constants and 1<a<4. The graph of y=f(x) in the xy-plane passes through points. (11,0) and (−2,0). If a is an integer, what could be the value of f(x)=ax2+bx+c0 ?
Identify Roots of Quadratic: Since the graph of f(x) passes through the points (11,0) and (−2,0), we can say that x=11 and x=−2 are roots of the quadratic equationax2+bx+c=0. We can use these roots to create two equations based on the fact that f(11)=0 and f(−2)=0.
Substitute Roots into Equation: Substituting x=11 into the equation gives us a(11)2+b(11)+c=0. This simplifies to 121a+11b+c=0.
Create System of Equations: Substituting x=−2 into the equation gives us a(−2)2+b(−2)+c=0. This simplifies to 4a−2b+c=0.
Eliminate Variable c: We now have a system of two equations with three unknowns:1) 121a+11b+c=02) 4a−2b+c=0We need one more equation to solve for a, b, and c. However, we are only asked to find the value of a+b, not the individual values of a, b, and c.
Solve for b in terms of a: We can eliminate c by subtracting the second equation from the first equation:(121a+11b+c)−(4a−2b+c)=0−0This simplifies to 117a+13b=0.
Find a+b: We can solve for b in terms of a by rearranging the equation:b=−13117ab=−9a
Determine Possible Values for a: Now we can find a+b by substituting b=−9a into the expression:a+b=a−9aa+b=−8a
Calculate Possible Values for a+b: Since 1 < a < 4 and a is an integer, the possible values for a are 2 and 3.
Final Answer: If a=2, then a+b=−8(2)=−16. If a=3, then a+b=−8(3)=−24.
Final Answer: If a=2, then a+b=−8(2)=−16. If a=3, then a+b=−8(3)=−24. Both −16 and −24 are possible values for a+b given the constraints on a. However, since the question asks for "what could be the value of a+b", we can provide any one of the possible values.