troubletrouble with factoring by grouping ab + 7b - 3a - 21

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hala718's profile pic

hala718 | High School Teacher | (Level 1) Educator Emeritus

Posted on

Given ab+7b - 3a - 21

We need to factor the equation.

==> We will write:

==> ( ab + 7b ) + ( -3a - 21)

Now we will factor b from the first two terms.

==> b*(a + 7) + ( -3a-21)

Now we will factor -2 from the last two terms.

==> b*(a+7) - 3*(a + 7).

Now we will factor ( a+ 7).

==> ( a+ 7) ( b -3)

giorgiana1976's profile pic

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted on

We also can re-group the terms:

ab + 7b - 3a - 21

(ab - 3a) + (7b - 21)

We'll factorize the 1st group by a:

a(b - 3) + (7b - 21)

We'll factorize the 2nd group by 7:

a(b - 3) + 7(b - 3)

We'll factorize by (b-3):

(b-3)(a+7)

The result of factorization is:

(b-3)(a+7)

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