Question

Multiply: (x – 4)(x + 5)

Answer 1

FOIL

$\mathbb{PROBLEM:}$

» Multiply: (x – 4)(x + 5)

• (a) x² + 5x - 20
• (b) x² - 4x - 20
• (c) x² - x - 20
• (d) x² + x - 20

$\mathbb{ANSWER:}$

• $\tt \color{hotpink} \bold{{x}^{2} + x- 20}$

— — — — — — — — — —

Solution:

• $\tt \bold{ F} \to (x – 4)(x + 5) = \blue{ {x}^{2} }$

• $\tt \bold{O } \to (x – 4)(x + 5) = \blue{ 5x}$

• $\tt \bold{ I} \to(x – 4)(x + 5) = \blue{ -4x}$

• $\tt \bold{L } \to (x – 4)(x + 5) = \blue{ - 20}$

So,

$\to \: \tt x {}^{2} + 5x - 4x - 20 \\ \tt \: = \underline{ \boxed{ \purple{ \tt{ {x}^{2} + x - 20 }}}}$

Hence, choice D is correct.

_______________❦︎_______________

Answer 2

Solution:

$\small\bold{(x – 4)(x + 5) }$

$\small\bold{ → x(x + 5) -4(x + 5) }$

$\small\bold{→ x2 + 5x – 4x – 20 }$

$\small\bold{ → x2 + x - 20 }$

Option (d) x2 + x - 20 is correct