if 1 and -2 are the zeroes of quadratic equation x²+ax+b=0 find a and b
Answers
Answer:
Step-by-step explanation:
1^2 +a(1)+b=0
1+a+b=0
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(-2)^2 +a(-2)+b=0
4-2a+b=0
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4-2a+(-1-a)=0
4-2a-1-a=0
3-3a=0
a=1
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1+1+b=0
b=-2
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Answer:
a= 1
b= -2
Step-by-step explanation:
As 1 and -2 are the zeroes of quadratic equation which means that these are the root values
which means that they are the values of x
Now
we have the equation
x² + ax + b = 0
Putting x = 1
1+ a(1)+b = 0
so
1+a+b = 0
a + b = -1
a = -1 - b ..........(i)
Now
x² + ax + b = 0
Putting x = -2
(-2)²+ a(-2)+b = 0
so
4-2a+b = 0
-2a + b = -4 .......(ii)
From equation (i) putting the value in equation (ii)
-2(-1 - b) + b = -4
2 + 2b + b = -4
3b + 2 = -4
subtracting -2 from both sides
3b + 2 - 2 = -4 - 2
3b = -6
Dividing both sides by 3
b = -2
Putting the value of b in equation (i)
a = -1 - b
Putting the vlaue of b
a = -1 - (-2)
a = -1 + 2
a = 1