$\bf \textit{difference of squares}
\\\\
(a-b)(a+b) = a^2-b^2\qquad \qquad 
a^2-b^2 = (a-b)(a+b)
\\\\\\
\textit{also recall that }i^2=-1\\\\
-------------------------------\\\\
\begin{cases}
x=-1+4i\implies &x+1-4i=0\\
x=-1-4i\implies &x+1+4i=0
\end{cases}
\\\\\\
(x+1-4i)(x+1+4i)=\stackrel{y}{0}
\\\\\\\
[(x+1)~~-~~(4i)][(x+1)~~+~~(4i)]=y
\\\\\\\
[(x+1)^2~~-~~(4i)^2]=0\implies (x^2+2x+1)~-~(4^2i^2)=y
\\\\\\
(x^2+2x+1)~-~(16\cdot -1)=y\implies (x^2+2x+1)~-~(-16)=y
\\\\\\
x^2+2x+1~~+16=y\implies x^2+2x+17=y$

3 0

4 years ago

Simplify: (x+7)(x-4)

SVETLANKA909090 [29]

Answer:

x² + 3x - 28

Step-by-step explanation:

Each term in the second factor is multiplied by each term in the first factor

(x + 7)(x - 4)

= x(x - 4) + 7(x - 4) ← distribute both parenthesis

= x² - 4x + 7x - 28 ← collect like terms

= x² + 3x - 28

6 0

3 years ago

At the market, 777 apples cost \$4.55$4.55dollar sign, 4, point, 55. how much do 999 apples cost? \$

vredina [299]

I divided $.55 by 777 and got 0.00585 cents per apple. Then I mulitplied 0.00585 by 999 and got $5.85.

6 0

3 years ago