(x+4)((x^2) - kx - 5) is expanded and simplified. The coefficient of the x^2 term twice the coefficient of the x term. Work out the value of k.
(x + 4) (x2 - kx - 5) = x3 - kx2 - 5x + 4x2 - 4kx - 20 = x3 + (4-k)x2 + (-5-4k)x - 20.The coefficients are: (4-k) of x2 and (-5-4k) of x. Now we can write the equation:(4-k) = 2(-5 - 4k) /expand4 - k = -10 - 8k /+8k4 + 7k = -10 /-47k = -14 /divide by 7k = -2
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Answered by Márk F. • Further Mathematics tutor
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