Question

Solve for x...........................

Answer 1

Answer:

Option A is correct, i.e. x = -3, x = 7.

Step-by-step explanation:

Given the equation is x² -4x -21 = 0.

We can compare it with general quadratic equation i.e. ax² +bx +c =0.

then a = 1, b = -4, c = -21.

We can use Quadratic formula as follows:-

x = ( -b ± √(b²-4ac) )/2a

x = ( +4 ± √(16-4*1*-21) )/2*1

x = ( +4 ± √(16+84) )/2

x = ( +4 ± √(100) )/2

x = ( +4 ± 10 )/2

x = (4+10)/2 or x = (4-10)/2

x = 14/2 or x = -6/2

x = 7 or x = -3

Hence, option A is correct, i.e. x = -3, x = 7.