X< 5 and (- infinity, 5 )
Answer:
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Answer:
Step-by-step explanation:
![\cos(2x) = \cos^2 x-\sin^2 x = 1-2\sin^2 x \\ \\ \cos(x) = 1-2\sin^2 (\frac{x}{2}) \\ \\ \Rightarrow \sin^2 (\frac{x}{2}) = \dfrac{1-\cos(x)}{2}\\ \\ \sin(\frac{x}{2}) = \pm \sqrt{\dfrac{1-\cos(x)}{2}},\quad x\in [\frac{3\pi }{2},\pi] \Rightarrow \frac{x}{2}\in [\frac{3\pi}{4},\frac{\pi}{2}]\\ \\ \Rightarrow \sin(\frac{x}{2}) > 0 \Rightarrow \sin(\frac{x}{2}) = \sqrt{\dfrac{1-(-\frac{3}{5})}{2}} \Rightarrow \sin(\frac{x}{2}) = \sqrt{\dfrac{8}{10}}=\dfrac{2\sqrt 2}{\sqrt{10}} = \\ \\ =\dfrac{2\sqrt 5}{5}](https://tex.z-dn.net/?f=%5Ccos%282x%29%20%3D%20%5Ccos%5E2%20x-%5Csin%5E2%20x%20%3D%201-2%5Csin%5E2%20x%20%5C%5C%20%5C%5C%20%5Ccos%28x%29%20%3D%201-2%5Csin%5E2%20%28%5Cfrac%7Bx%7D%7B2%7D%29%20%5C%5C%20%5C%5C%20%5CRightarrow%20%5Csin%5E2%20%28%5Cfrac%7Bx%7D%7B2%7D%29%20%3D%20%5Cdfrac%7B1-%5Ccos%28x%29%7D%7B2%7D%5C%5C%20%5C%5C%20%5Csin%28%5Cfrac%7Bx%7D%7B2%7D%29%20%3D%20%5Cpm%20%5Csqrt%7B%5Cdfrac%7B1-%5Ccos%28x%29%7D%7B2%7D%7D%2C%5Cquad%20x%5Cin%20%5B%5Cfrac%7B3%5Cpi%20%7D%7B2%7D%2C%5Cpi%5D%20%5CRightarrow%20%5Cfrac%7Bx%7D%7B2%7D%5Cin%20%5B%5Cfrac%7B3%5Cpi%7D%7B4%7D%2C%5Cfrac%7B%5Cpi%7D%7B2%7D%5D%5C%5C%20%5C%5C%20%5CRightarrow%20%5Csin%28%5Cfrac%7Bx%7D%7B2%7D%29%20%3E%200%20%5CRightarrow%20%5Csin%28%5Cfrac%7Bx%7D%7B2%7D%29%20%3D%20%5Csqrt%7B%5Cdfrac%7B1-%28-%5Cfrac%7B3%7D%7B5%7D%29%7D%7B2%7D%7D%20%5CRightarrow%20%5Csin%28%5Cfrac%7Bx%7D%7B2%7D%29%20%3D%20%5Csqrt%7B%5Cdfrac%7B8%7D%7B10%7D%7D%3D%5Cdfrac%7B2%5Csqrt%202%7D%7B%5Csqrt%7B10%7D%7D%20%3D%20%5C%5C%20%5C%5C%20%3D%5Cdfrac%7B2%5Csqrt%205%7D%7B5%7D)
#1. 4x^2 + 17 - 15 = 0
Use the roots given, and plug them in to a factored form. Then, foil! It can also be helpful to multiply the equation to get rid of decimals/fractions.
(x - 3/4)(x + 5) = 0
x^2 - 3/4x + 5x - 3 3/4 = 0
x^2 + 4.25 - 3.75 = 0 (multiply everything by 4)
4x^2 + 17 - 15 = 0
#2. y = 0, -4
Both 4y^2 and 16y contain a 4 in the coefficient and a y in the variables. Therefore, we can factor out a 4y from each.
4y(y + 4) = 0
Then, set both parts of the factored equation equal to 0.
4y = 0
y = 0
y + 4 = 0
y = -4
#3. a = 0, -3
Both 6a^5 and 18a^4 contain a 6 in the coefficient and an a in the variables. Therefore, we can factor out a 6a^4 from each.
6a^4(a + 3) = 0
Then, set both parts of the factored equation equal to 0.
6a^4 = 0
a = 0
a + 3 = 0
a = -3
#4. x = -8
We are looking for two terms that multiply to equal a * c, and add up to equal b. We know that 8 + 8 = 16, and 8 * 8 = 64. There are no negatives in this equation, therefore both signs in our factored form are positive.
(x + 8)(x + 8) = 0
x + 8 = 0
x = -8
#5. x = -8, 8
First, subtract 64 from both sides. The key word here is 'factoring.' If this was not present, there is a different way (which may be easier for some).
x^2 = 64
x^2 - 64 = 0
Next, use the difference of two squares property to factor (x - c)(x + c), and set the two binomials equal to 0.
(x - 8)(x + 8) = 0
x - 8 = 0
x = 8
x + 8 = 0
x = -8
Hope this helps!! :)
Answer:
24 Lawns
Step-by-step explanation: If it took 10 hours to mow 8 lawns, then add 8 to its self 3 times and you get 24.
