Question 5
Which of the following equations has the sum of its roots as 3?
(a) 2x2−3x+6=0
(b) −x2+3x−3=0
(c) √2x2−3√2x+1=0
(d) 3x2−3x+3=0
a) Given that, 2x2−3x+6=0
On comparing with ax2 + bx + c = 0, we get
a = 2, b = 3 and c = 6
Sum of the roots =−ba=−(−3)2=32
So, sum of the roots of the quadratic equation 2x2 – 3x + 6 = 0 is not 3, so it not the answer
b) Given that, −x2 + 3x – 3 = 0
On compare with ax2 + bx + c = 0, we get
a = -1, b = 3 and c = - 3
∴ sum of the roots =−ba=−(3)−1=3
So, sum of the roots of the quadratic equation −x2+3x–3 is 3, so it is the answer.
c) Given that √2x2−3√2x+1=0
⇒2x2−3x+√2=0
On comparing with ax2 + bx + c = 0, we get
a = 2, b = - 3 and c = √2
sum of the roots =−ba=−(−3)2=32
So, sum of the roots of the quadratic equation √2x2−3√2x+1=0 is not 3, so it is not the answer.
d) Given that, 3x2 – 3x + 3 = 0
⇒x2−x+1=0
On comparing with ax2 + bx + c = 0 get
a = 1, b = - 1 and c = 1
sum of the roots =−ba=−(−1)1=1
So, sum of the roots of the quadratic equation 3x2 - 3x + 3 = 0 is not 3, so it is not the answer.