3. Let f (x) = the square of 2x-7, find the values of F (- 1), f (5), f (a), f (x + H) 1. Let f (x) = the square of 2x-7, find the values of F (- 1), f (5), f (a), f (x + H)

3. Let f (x) = the square of 2x-7, find the values of F (- 1), f (5), f (a), f (x + H) 1. Let f (x) = the square of 2x-7, find the values of F (- 1), f (5), f (a), f (x + H)

Let f (x) = the square of 2x-7,
f（﹣1）=2×（-1）²-7=2-7=-5；
,f（5）=2×5²-7=50-7=43；,
f（a）=2a²-7,
f（x＋h）=2（x+h）²-7；
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(X)　＝x2－2x　＋　2a(a2-2ab-b2)-b(2a2 ab-b2)
Ψ 2Ab / a B ≤ 2Ab / 2 √ AB = √ AB m ＜ 0, n ＜ 0, find (√ - M) 2 (√ - n) 2

Three vectors AB, BC and Ca constitute ABC, AB BC CA = 0 (M 1) x2-mx M-1 > 0, assuming be = BC CE = BC Ca / 2; CF = CA AF = CA AB / 2, assuming three vectors AB, BC and Ca constitute ABC, AB BC CA = 0

In RT (triangle) ABC, angle c = 90 ', if AB = 5, BC = 3, what is the value of SINB?

Angle c = 90 degrees, ab = 5, BC = 3
Then: AC = (5 ^ 2-3 ^ 2) ^ (1 / 2) = 4
sinB=AC/AB=4/5

When is 3:40

Three and two-thirds is equal to 3.66

Calculate the perimeter and area of the playground below (50m wide and 100m long)

Perimeter: (50 + 100) * 2 = 300m
Area: 50 * 100 = 5000 square meters

In the triangle ABC, if a is 60 degrees and BC = 3, then the circumference of the triangle is? And the answer contains angle B

From the sine theorem, we have
BC/sinA=AC/sinB=AB/sinC
AC = bcsinb / Sina = 3sinb / sin60 ° = 3sinb / (√ 3 / 2) = 2 √ 3sinb
AB=BCsinC/sinA=BCsin[180°-(A+B)]/sinA=3sin(60°+B)/sin60°
=(3sin60°cosB+3sinBcos60°)/sin60°
=3cosB+3sinBcot60°
=3cosB+√3sinB
AB+BC+AC=3cosB+√3sinB+3+2√3sinB=3√3sinB+3cosB+3
The perimeter of Δ ABC is 3 √ 3sinb + 3cosb + 3

Let x square plus y square minus 2x plus 4Y = 0, and prove that the maximum value of x minus 2 is 0
Thank you

X ^ 2 + y ^ 2-2x + 4Y = 0, (x-1) ^ 2 + (y + 2) ^ 2 = 5 let x = 1 + root 5cos θ, y = - 2 + root 5sin θ
Isn't that right?

Is the light pollution caused by the glass curtain wall of high-rise buildings due to the diffuse reflection of light?

No, the surface of the glass curtain wall is flat, it is specular reflection. The diffuse reflection requires rough surface

Ancient water clocks can be divided into () and ()?

Ancient water clocks can be divided into two types: discharge type and receiving type

Given: x = (√ 5-1) / 2, find the value of x ^ 5-5x
Don't bring it in directly. Can we use other methods

2x+1=√5
square
4x²+4x+1=5
x²=1-x
square
x^4=1-2x+x²
=1-2x+(1-x)
=2-3x
So x ^ 5 = x * x ^ 4
=x(2-3x)
=2x-3x²
=2x-3(1-x)
=5x-3
So the original formula = 5x-3-5x = - 3