x ( x + 4 ) = 21
To solve this equation , we should first distribute the " x "
By distributing the " x " , you should get
x^2 + 4x = 21 now we can subtract 21 on both sides
By subtracting 21 on both sides , you would get
x^2 + 4x - 21 = 0 Now we can factor ( such as using the x factor which means having two numbers that would have a product of -21 and a sum of 4 )
By factoring the equation , you would get
( x + 7 ) ( x - 3 ) This is just basically x + 7 = 0 and x - 3 = 0
So your answer is x = -7 or 3
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