Question

The roots of the equation x2 + 4x – 21,
21,= 0 are
a) (7,3)
b) (-7,3)
c)(-7, -3)
d) (7,-3)​

Answer 1

Answer:

b) -7,3

Step-by-step explanation:

x^2+4x-21

x^2 +7x-3x-21

x(x+7)-3(x+7)

(x-3)(x+7)

x-3=0 ,. x+7=0

x=3 or x= -7

So Option b) -7,3 is correct

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Answer 2

Answer:

b) (-7,3)

Step-by-step explanation:

x^2+4x-21=0

x^2 +7x -3x -21 (4x is split as 7x-3x, so as to satisfy the condition 7*-3=21 ans 7-3=4.i.e,in a equation x^2+bx+c, b is split in such a way that the sum o those numbers=b and product=c.)

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

taking x common in first 2 terms and -3 common in the next 2 terms

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

Now taking (x+7) common,

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

Now equating each term to 0 we get the roots

so, x+7=0 and x-3=0

Hence, roots are x=-7 and x=3

So, roots are, (-7,3)