Question

20. If and-3 are the zeros of the quadratic polynomial ax? +7x+b then
3
find the values of a and b.
[CBSE 2011]
ANSWERS (EXERCISE 2A)​

Answer 1

Correct QuestioN :

If x=2/3 and x=-3 are the roots of eq ax2+7x+b=0 find values of a and b.

SolutioN :

• Zeros is x = 2 / 3 , - 3.

$\tt \dagger \: \: \: \: \: \bigg( x = \dfrac{2}{3} \bigg) \bigg(x = - 3 \bigg)$

$\tt \dagger \: \: \: \: \: \bigg( x = \dfrac{2}{3} \bigg) \bigg(x = - 3 \bigg) =0 .$

$\tt \dagger \: \: \: \: \: \bigg( x - \dfrac{2}{3} = 0. \bigg) \bigg(x + 3 = 0. \bigg)$

$\tt : \implies \bigg( x - \dfrac{2}{3} \bigg)(x + 3 )= 0.$

$\tt : \implies 3 {x}^{2} - 2x + 9x - 6 = 0.$

$\tt : \implies 3 {x}^{2} + 7x - 6 = 0.$

✎ Compare With given Quadratic Equation.

☛ ax² + bx + c = 0.

ax² + 7x + b = 0.

Where as,

• a = 3.
• b = 7.
• c = - 6.

✡ Therefore, the value of a is 3 , b is - 6.

Answer 2

Answer:

Hope this helps you ✌️✌️