Q.>if x= 2/3 and x= -3 are the roots of the equation ax2 +7x+b=0, find the value of a and b.

Given, and x = – 3 are the roots of the quadratic equation .

...(1)

Putting in equation (1), we get

Putting x = – 3 in equation (1), we get

⇒ 9a – 21 + b = 0

⇒ 9a + b = 21

b = 21 – 9a ...(3)

Solving (2) and (3), we get

4a + 9 ( 21 – 9a) = – 42

⇒ 4a + 189 – 81a = – 42

⇒ –77a = – 42 – 189 = – 231

a = 3

Putting the value of a in (3), we get

b = 21 – 9 × 3 = 21 – 27 = – 6

Thus, the value of a and b is 3 and – 6 respectively.

  • 129

 its ax(square) the questions is not displaying properly.

  • -20

a=3

b=-6

post again if u want the full solution

  • -13

When x = 2/3

then ,

4/9 a +14/3 + b = 0 

by making LCM equal,

4a + 42 + 9b = 0 ..............(1)

When x = -3

then, 

9 a - 21 + b = 0 ..............(2)

 from eq. 1 and 2

4a +42 + 9b = 0

9a -21 +b = 0

now by elimination method,

4a +42 + 9b = 0

81a - 189 + 9b = 0

now by substracting both  the eq.,

4a - 81a + 231 + 9b - 9b = 0

77 a +231 = 0

77a = -231 

a = -33

and 4a + 42 + 9b = -132 +42 + 9b 

= -90 + 9 b 

b = 90/9 = 10

HOPE THIS HELPS...

  • -8
What are you looking for?