Answer:
a = 1, b = -2
Step-by-step explanation:
You are given values of x are 1 and 2 when the equation is 0
To solve the problem substitute the values of x into the equation
For x =1
1^2 + a(1) + b = 0
1 + a + b = 0
a+b = -1(call this equation i)
For x = -2
-2^2 + a(-2) + b = 0
4 - 2a + b = 0
-2a + b = -4 (call this equation ii)
Now solve equation i and ii simultaneously to get values of a and b.
a+b = -1
-2a+b = -4
By elimination method (also you can solve by substitution method) subtract equation ii from equation i, we get
3a = 3
Divide 3 both sides, you get
a = 1
Take the value of a above substitute it into either equation i or ii to get the value of b
Here i considered equation i
a + b = -1
1 + b = - 1
b = - 1 - 1
b = -2
Therefore a = 1, b = -2
