Writing A Quadratic Equation Given The Roots And The Leading Coefficient Calculator

Peg G.

asked • 10/03/17

writing a quadratic equation given the roots and the leading coefficient

Write the quadratic equation whose roots are 3 and -5, and whose leading coefficient is 3.

(use the letter x to represent the variable)

Answer= _____ =0

I do know how to do the first half but I have trouble with the second half! Please help! Thanks in advance!

I do not know what to do after

3 (x-3)(x+5)

What do you to get the next step?

1 Expert Answer

Kenneth S. answered • 10/03/17

Expert Help in Algebra/Trig/(Pre)calculus to Guarantee Success in 2018

You're just asking for the last step. The answer is to multiply it out.

Use FOIL to multiply the two binomials, then distribute the leading coefficient (3). DONE.

Peg G.

okay, so when doing FOIL for this problem how do you do it? What are the numbers that you multiply (etc). I still don't understand how to FOIL this correctly.

Kenneth S.

(a+b)(c+d) = (a+b)c + (a+b)d = c(a+b) + d(a+c) =ac + bc + ad + cd

THIS IS THE GENERAL RULE, PROVED.

FOIL tells you multiply the two 'firsties', then the two outer elements, then the two inners, and finally the two lasts:

F: ab

O: ad

I: bc

L: bd

When you do it, include the signs.

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