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)2 - 4 - 21 = 0 SImplified, so all x's are on one side of the equation: (x+2)2 = 25, Removing square root, DONT FORGET "±" : (x+2) = ± 5, Solve for two solutions: x = 3, x = -7
CS
Related Maths A Level answers
All answers ▸Use implicit differentiation to find the derivative of 2yx^2, with respect to x.
How do I deal with parametric equations? x = 4 cos ( t + pi/6), y = 2 sin t, Show that x + y = 2sqrt(3) cos t.
Complete the indefinite integral : ∫x lnx dx
Prove the identity (sin2x)/(1+(tanx)^2) = 2sinx(cosx)^3