Question

Multiply: (x – 4)(x + 5)

(a) x2 + 5x - 20

(b) x2 - 4x - 20

(c) x2 - x - 20

(d) x2 + x - 20​

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

`\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