The maximum value of the function y = cosx-4cos (x / 2) is

The maximum value of the function y = cosx-4cos (x / 2) is

y=cosx-4cos(x/2)
=2cos^2(x/2)-1-4cos(x/2)
=2(cos(x/2)-1)^2-3
And - 1

Finding the maximum and minimum of the function y = 7-4sinxcosx + 4cosx-4cos4x

ymax=12 ymin=8

Y = the fourth power of cosx - the fourth power of SiNx to find the maximum and minimum (detailed process)

Y = the fourth power of cosx - the fourth power of SiNx
=(cos²x+sin²x)(cos²x-sin²x)
=1*cos2x
=cos2x
Maximum = 1
Minimum = - 1

Wang teacher out of such a problem: known a = 2013 - 2 power, B = (- 2012) &#, find the algebraic formula
（a-3b)²-2a（a-7b）+（a+b）(a-9b）+1,

（a-3b)²-2a（a-7b）+（a+b）(a-9b）+1,
=a^2-6ab+9b^2-2a^2+14ab+a^2-8ab-9b^2+1
=1

Buy three kinds of fruit 30 kg, share 80 yuan. Among them, apple 4 yuan per kg, Orange 3 yuan, pear 2 yuan?
No hurry

Suppose the apple has x kg, the orange has y kg and the pear has Z kg
1.4X+3Y+2Z=80
2.X+Y+Z=30
2 times 3 goes to 1
So we get x = Z-10
It can be seen that pears weigh 10 jin more than apples
It's only 30 jin in all
It can be calculated
0

3A = 2B, what's the proportion of a and B? 2 / x = 3 / y, what's the proportion of X and y? Please explain the reason!

3a=2b
a：b=2:3
A is proportional to B
X of 2 = 3 of Y
xy=6
In inverse proportion

The imaginary number Z satisfies Z ^ 3 = 8, Z ^ 3 + Z ^ 2 + 2Z + 2=

z^3=8
(Z-2) (Z ^ 2 + 2Z + 4) = 0 because Z is an imaginary number
z^2+2z+4=0
z^3+z^2+2z+2=z^3+(z^2+2z+4)-2=z^3-2=8-2=6

There are 700kg apples in the fruit shop, 150g less than pears. The weight of apples is several times that of pears, and the weight of pears is several times that of apples
List the formulas
That's 150 grams

700 + 150 = 850 kg
700/850=15/17
850 / 700 = 17 / 15 times

The product of multiplication of two numbers is 1 and 5 / 23, one of which is 1 and 3 / 69. How much is the other number?

7/6

Let's describe Tellegen's theorem in detail

Tellegen theorem 1 for a circuit with n nodes and B branches, suppose that the current and voltage of each branch take the associated reference direction, and let (I1, I2, ···, IB) and (U1, U2, ···, UB) be the current and voltage of B branches respectively, then for any time t, there is I1 * U1 + I2 * U2 + ··· + IB