# The factors of the trinomial 6 y 2 + 11 y − 21 . ### Precalculus: Mathematics for Calcu...

6th Edition
Stewart + 5 others
Publisher: Cengage Learning
ISBN: 9780840068071 ### Precalculus: Mathematics for Calcu...

6th Edition
Stewart + 5 others
Publisher: Cengage Learning
ISBN: 9780840068071

#### Solutions

Chapter 1.3, Problem 70E
To determine

## To calculate: The factors of the trinomial 6y2+11y−21 .

Expert Solution

The factors of the trinomial 6y2+11y21 are 6y7 and y+3 .

### Explanation of Solution

Given information:

The expression 6y2+11y21 .

Formula used:

To find the factor of the trinomial of the form ax2+bx+c , find the numbers p,q,r and s such that sum of product of two numbers is equal to coefficient of x (ps+qr=b) , product of p and q is equal to the coefficient of x2 pq=a and product of r and s numbers is equal to constant term (rs=c) , such that (px+r) and (qx+s) are the factors of ax2+bx+c .

ax2+bx+c=pqx2+(ps+qr)x+rs=pqx2+psx+qrx+rs=px(qx+s)+r(qx+s)=(px+r)(qx+s)

Calculation:

Consider the given expression 6y2+11y21 .

Recall that to find the factor of the trinomial of the form ax2+bx+c , find the numbers p,q,r and s such that sum of product of two numbers is equal to coefficient of x (ps+qr=b) , product of p and q is equal to the coefficient of x2 (pq=a) and product of r and s numbers is equal to constant term (rs=c) , such that (px+r) and (qx+s) are the factors of ax2+bx+c .

ax2+bx+c=pqx2+(ps+qr)x+rs=pqx2+psx+qrx+rs=px(qx+s)+r(qx+s)=(px+r)(qx+s)

So, find p,q,r and s such that pq=6 , ps+qr=11 and rs=21 .

Here, p=6 , q=1 , r=7 and s=3 , so, 6y2+11y21 will be factorized as,

6y2+11y21=6y2+(187)y+(7)(3)=6y2+18y7y21=6y(y+3)7(y+3)=(6y7)(y+3)

Thus, the factors of trinomial 6y2+11y21 are 6y7 and y+3 .

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