SOLUTION: Andrew factored the expression28x^2-42x^2+35x as 7x(4x^2+6x-5) . But when Melissa applied the distributive law and multiplied out7x(4x^2+6x-5) , she got28x^3+24x^2-23x ; thus, Andr

Question 489000: Andrew factored the expression28x^2-42x^2+35x as 7x(4x^2+6x-5) . But when Melissa applied the distributive law and multiplied out7x(4x^2+6x-5) , she got28x^3+24x^2-23x ; thus, Andrew�s solution does not appear to check. Why is that? Please help Andrew to understand this better. Explain your reasoning and correctly factor the original expression, if possible. If the expression is prime, so state
Answer by MathLover1(20849) (Show Source): You can put this solution on YOUR website!

Andrew factored the expression
as .
But when Melissa applied the distributive law and multiplied out7x(4x^2+6x-5) , she got
;

let's check first Melisa's result:

....she made these mistakes when multiplied : for she got ...( and

but, Andrew�s solution does not check either because he made mistake with a sign
in expression coefficients are (positive), (negative), and (positive)
so, instead of , he should have

I hope Andrew will understand this better now. So, be careful with the signs and do a quick check that the distributive law takes you back to the expression you started with.
correctly factored original expression:

If the expression is prime: It isn't prime if it have factors besides 1 and itself.
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