We are given a quadratic function $g(x) = ax^2 + bx + 1$. We are also given that $g(1) = 0$ and $g(2) = 3$. We need to find two equations in terms of $a$ and $b$, and then solve these equations to find the values of $a$ and $b$.

AlgebraQuadratic FunctionsSystems of EquationsSubstitutionElimination
2025/3/12

1. Problem Description

We are given a quadratic function g(x)=ax2+bx+1g(x) = ax^2 + bx + 1. We are also given that g(1)=0g(1) = 0 and g(2)=3g(2) = 3. We need to find two equations in terms of aa and bb, and then solve these equations to find the values of aa and bb.

2. Solution Steps

First, use the given information g(1)=0g(1) = 0:
g(1)=a(1)2+b(1)+1=0g(1) = a(1)^2 + b(1) + 1 = 0
a+b+1=0a + b + 1 = 0
a+b=1a + b = -1 (Equation 1)
Next, use the given information g(2)=3g(2) = 3:
g(2)=a(2)2+b(2)+1=3g(2) = a(2)^2 + b(2) + 1 = 3
4a+2b+1=34a + 2b + 1 = 3
4a+2b=24a + 2b = 2
2a+b=12a + b = 1 (Equation 2)
Now we have two equations:
Equation 1: a+b=1a + b = -1
Equation 2: 2a+b=12a + b = 1
We can solve this system of equations using substitution or elimination. Let's use elimination. Subtract Equation 1 from Equation 2:
(2a+b)(a+b)=1(1)(2a + b) - (a + b) = 1 - (-1)
2a+bab=22a + b - a - b = 2
a=2a = 2
Now substitute a=2a = 2 into Equation 1:
2+b=12 + b = -1
b=12b = -1 - 2
b=3b = -3
So, a=2a = 2 and b=3b = -3.

3. Final Answer

a=2a = 2 and b=3b = -3.