Given that the coefficient of $$$x^{2}$$$ in the expansion of $$$(1-3 x)(1+a x)^{6}$$$ is $$$-3$$$, find the possible values of the constant $$$a$$$. .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... ....................................................................................................................................................

Mathematics

IGCSE&ALevel

CAIE

Exam No：9709_w21_qp_13 Year：2021 Question No：2(b)

Answer:

their $15 a^{2} \pm(3 \times$ their $6 a)$
$15 a^{2}-18 a=-3$
$(3)(a-1)(5 a-1)[=0]$
$a=1, \frac{1}{5}$

Knowledge points:

1.1.3 solve quadratic equations, and quadratic inequalities, in one unknown (By factorising, completing the square and using the formula.)

1.6.1 use the expansion of , where is a positive integer (Including the notations and n!) (Knowledge of the greatest term and properties of the coefficients are not required.)

Answer:

Knowledge points:

Solution:

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