General form of Quadratic Equation
aX²+bX+c=0
Quicker Math tricks |
Quadratic Equation has two roots.
Usually we denote the two roots of Quadratic Equation by the symbol α and β
In the equation
aX²+bX+c=0 if α and β are the two roots then what is the value of α+ β?
Quicker tricks
α+ β=-b/a
Example-1:if α and β are the two roots of 3X²+2X+1=0 then what is the value of α+ β?
Then α+ β =-b/a
=-2/3
Example-2:if α and β are the two roots of 3X²+2X+1=0 then what is the value of αβ?
3X²+2X+1=0 if α and β are the two roots
αβ=c/a
=1/3
Example-3:if α and β are the two roots of 3X²+2X+1=0 then what is the value of 1/α+1/β?
3X²+2X+1=0 if α and β are the two roots
1/α+1/β =-b/c
=-2/1=-2
Example-4:if α and β are the two roots of 3X²+2X+1=0 then what is the value of α²+β²?
3X²+2X+1=0 if α and β are the two roots
α²+β² =(α+ β)² -2αβ
=(b² -2ac)/a²
=(2² -2×3×1)/3²
=(4-6)/9=-2/9
If α and β are the two roots of
aX²+bX+c=0 then
α-²+β-²=(b² - 2ac)/c²
Example-5:if α and β are the two roots of 3X²+2X+1=0 then what is the value of α-²+β-²?
α-²+β-²=(b² - 2ac)/c²
=(2² -2×3×1)/1²
=(4-6)/1=-2/1
=-2
Example-6:if α and β are the two roots of 3X²+2X+1=0 then what is the value of
(α+1)(β+1)?
(α+1)(β+1)=αβ+α+ β+1
=(a+c-b)/a
=(3+1-2)/3
=2/3
If α and β are the two roots of
aX²+bX+c=0 and the two roots are multiplicative inverse to each other then
αβ=1
c/a=1
c=a
If α and β are the two roots of
7X²+5X+c=0 and the two roots are multiplicative inverse to each other then what is the value of c?
c=7
If α and β are the two roots of
aX²+bX+c=0 and the two roots are additive inverse to each other then
α+β=0
-b/a=0
b=0
Example :
If α and β are the two roots of
5X²+(k+3)X+1=0 and the two roots are additive inverse to each other then what is the value of k?
Solution -
K+3=0
k=-3
If the product and sum of two roots of aX²+bX+c=0 are same
Then -b=c
If the product and sum of two roots of 9X²+pX+4=0 are same then what is the value of p?
Solution -
P=-4
If one root of aX²+bX+c=0 is n times the other root then
nb²=(n+1)² ac
Example:If one root of pX²+2X+1=0 is 3 times the other root then what is the value of p?
Solution -
3(2)²=(3+1)² p×1
12=16p
p=12/16=3/4
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