Question

solve this two please
solve the quadratic equation
10th grade​

Answer 1

Answer:

x=7  or   x=-3

Step-by-step explanation:

x²-4x-21=0

x²+3x-7x-21=0

x(x+3)-7(x+3)=0

(x-7)(x+3)=0

x=7  or   x=-3

Answer 2

Answer:

(i) Given,

p(x) = x^2 - 4x - 21

=> x^2 - 4x - 21 = 0

On using the splitting term method, we get,

=> x^2 - 7x + 3x - 21 = 0

=> x(x - 7) + 3(x - 7) = 0

=> (x + 3)(x - 7) = 0

Here,

either (x + 3) = 0 or (x - 7) = 0

Then, for the values of x :

(x + 3) = 0

=> x = -3

(x - 7) = 0

=> x = 7

Hence,

x = -3 , 7

(ii) On solving the given equation, we get,

1/x-3 - 1/x+5 = 1/6

x+5-x+3/x²+2x-15= 1/6 (taking lcm)

8/x²+2x-15= 1/6

on cross multiplication

8*6=x²+2x-15

x²+2x-15-48=0

x²+2x-63=0

x²+(9x-7x) -63=0

x²+9x-7x-63=0

x(x+9)-7(x+9)=0

(x+9)(x-7)=0

x= -9 , x=7

Hence, x = -9 , 7