Question 43

Coefficient of $$x^2$$ in (x + 3)(2 - 4x)(5x - 6)  is

Solution

A coefficient is a numerical or constant quantity placed before and multiplying the variable in an algebraic expression. Eg : In $$ax^2$$, coefficient is $$a$$

Expression : $$(x + 3)(2 - 4x)(5x - 6)$$

= $$(2x - 4x^2 + 6 - 12x)(5x - 6)$$

= $$(-4x^2 - 10x + 6)(5x - 6)$$

= $$5x(-4x^2 - 10x + 6) - 6(-4x^2 - 10x + 6)$$

= $$-20x^3 - 50x^2 + 30x + 24x^2 + 60x - 36$$

= $$-20x^3 - 26x^2 + 90x - 36$$

$$\therefore$$ Coefficient of $$x^2$$ = -26

=> Ans - (D)


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