(3x+5)(x+4)?

3 x ² + 12 x + 5 x + 20
3 x ² + 17 x + 20

3x(x) + 3x(4) + 5(x) + 5(4) =
3x² + 12x + 5x + 20
= 3x² + 17x + 20
~~~

the answer is 3x^2 + 5x + 12x + 20
simplify so the final answer is 3x^2 + 17x + 20 = 0

(3x+5)(x+4)

Use the foil method.
Firft
Outer
Inner
Last
multiply each term by the other terms.

3x*x=3x^2
3x*4=12x
5*x=5x
5*4=20

The answer is:
3x^2+12x+5x+20

simplifies to:
3x^2+17x+20

Apply Foil:

(3x+5)(x+4) = 3x*x+3*4x+5*x+5*4 = 3x^2+12x+5x+20 = 3x^2+17x+20

3x^2 +5x +12x +20
= 3x^2 +17x +20

(3x+5)(x+4)
3x * x + 5x + 12x + 20
3x^2 + 17x + 20

(3X+5)(x+4)
= (3X x X) + (5 x X) + (3X x 4) + (5 x 4)
= 3X^2 + 5X + 12X + 20
= 3X^2 + 17X + 20

X= unknown
x = multiply

Have you heard of F.O.I.L. ?
It refers to First Outside Inside and Last .
Multiply the first terms in both brackets:

3x times x = 3x^2

then multiply the 'outside' terms:

3x times 4 = 12x

now multiply the 'inside' terms:

5 times x = 5x

and lastly, multiply the Last terms in each bracket:

5 times 4 = 20

Collecting like terms yields the following trinomial expression:

3x^2 + 17x + 20