Question

7x^2+49x +84=0 solve the quadratic equation ​

Answer 1

Answer:

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Answer 2

Step-by-step explanation:

1st method-

2x + 4 = 10

2x = 6

x = 3

2nd method-

Subtract 4 from both sides

we get 2x = 6

x= 3

3rd method-

Square both sides

(2x+4)2=102

4x2+16x+16=100 {as we know (a+b)2=a2+2ab+b2 }

4x2+16x−84=0

4x2+28x−12x−84=0 (by factorisation)

4x(x+7)−12(x+7)=0

(4x−12)(x+7)=0

4x=12 or x=−7

x=3 or x=−7

We put 1st value of x in LHS, 2(3)+4 = 10

We put 2nd value of x in LHS, 2(-7)+4 = -10

So 2nd value of x should not be considered

Hence answer is 3