$(3-4i)(a+bi)=25\qquad\text{use FOIL method}\\\\(3)(a)+(3bi)+(-4i)(a)+(-4i)(bi)=25+0i\\\\3a+3bi-4ai-4bi^2=25+0i\\\\3a+3bi-4ai-4b(-1)=25+0i\\\\3a+3bi-4ai+4b=25+0i\\\\(3a+4b)+(3b-4a)i=25+0i\\.\qquad\qquad\qquad\qquad\Downarrow\\\\3a+4b=25\ and\ 3b-4a=0\\\\3b-4a=0\qquad\text{add 4a to both sides}\\\\3b=4a\qquad\text{divide both sides by 3}\\\\b=\dfrac{4}{3}a\qquad\text{substitute it to the first equation}\\\\3a+4\left(\dfrac{4}{3}a\right)=25\\\\3a+\dfrac{16}{3}a=25\qquad\text{multiply both sides by 3}$

$9a+16a=75\\\\25a=75\qquad\text{divide both sides by 25}\\\\\boxed{a=3}\qquad\text{put the value of a to}\ b=\dfrac{4}{3}a:\\\\b=\dfrac{4}{3}(3)\\\\\boxed{b=4}\\\\Answer:\ \boxed{(3-4i)\underline{(3+4i)}=25}$

6 0

3 years ago

1. List the domain and range of the relation

Naddik [55]

Answer:

Domain: {(7, 9, 0)}

Range: {(-2, 9, 11, 2)}

3 0

3 years ago

Tangent line of f(x) = sec x @ (pi/3, 2)

Dmitry_Shevchenko [17]

The derivitive of sec(x) is sec(x)tan(x)

find the slope at pi/3

sec(pi/3)=2
tan(pi/3)=√3

sec(x)tan(x) at x=pi/3 is 2√3

for slope=m and a point is (x1,y1)
the equation is
y-y1=m(x-x1)
slope=2√3
point=(pi/3,2)

equation is
y-2=2√3(x-pi/3)

3 0

3 years ago

Explain why a triangle can't have two right angles​

Explain why a triangle can't have two right angles