Using the "complete the square" method, solve the following x^2 +4x - 21 =0

x2+4x-21= 0,  This can be factorised into brackets as shown: (x+2)- 4 - 21 = 0 SImplified, so all x's are on one side of the equation: (x+2)= 25, Removing square root, DONT FORGET "±" : (x+2) = ± 5,  Solve for two solutions: x = 3, x = -7

Answered by Charlotte S. Maths tutor

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