Answer:
Because they are
Step-by-step explanation:
they ar4
You can use Substitution to solve this problem:
4x-y=20
-y=-4x+20
y=4x-20
Now you have two equations, and you use the first one to substitute into the second one.
y=4x-20 and -2x-2y=10
-2x-2(4x-20)=10
-2x-8x+40=10
-10x+40=10
-10x=-30
-x=-3
x=3
Now that we have figured out what x is, we can substitute x in to one of the equations to figure out y.
4x-y=20 x=3
4(3)-y=20
12-y=20
-y=8
y=-8
<em><u>So your answer would be x=3 and y=-8</u></em>
Answer:
23.92
Step-by-step explanation:
You can round 2.99 to 3 and do 3x8 mentally then subtract 8 cents ¯\_(ツ)_/¯
78
because 5 times 2 equals 10 so then u times 39 times 2 and get 78
T=-1
sinA=sin(π/2-3A), A=2nπ+π/2-3A, 4A=2nπ+π/2, A=nπ/2+π/8 where n is an integer.
Also, π-A=2nπ+π/2-3A, 2A=2nπ-π/2, A=nπ-π/4.
The hard way:
cos3A=cos(2A+A)=cos(2A)cosA-sin(2A)sinA.
Let s=sinA and c=cosA, then s²+c²=1.
cos3A=(2c²-1)c-2c(1-c²)=c(4c²-3).
s=c(4c²-3) is the original equation.
Let t=tanA=s/c, then c²=1/(1+t²).
t=4c²-3=4/(1+t²)-3=(4-3-3t²)/(1+t²)=(1-3t²)/(1+t²).
So t+t³=1-3t², t³+3t²+t-1=0=(t+1)(t²+2t-1).
So t=-1 is a solution.
t²+2t-1=0 is a solution, t²+2t+1-1-1=0=(t+1)²-2, so t=-1+√2 and t=-1-√2 are solutions.
Therefore tanA=-1, -1+√2, -1-√2 are the three solutions from which:
A=-π/4, π/8, -3π/8 radians and these values +2πn where n is an integer.
Replacing π by 180° converts the solutions to degrees.
