Answer:
Step-by-step explanation:
Use FOIL method
1) (x +4 )(3x +2) = x*3x + x*2 + 4*3x + 4*2
= 3x² + 2x + 12x + 8
= 3x² + 14x + 8
4) (4x - 1) (2x + 7) = 4x*2x + 4x*7 + (-1)*2x + (-1) * 7
= 8x² + 28x - 2x - 7
= 8x² + 26x - 7
What is the value of x in the equation 4(7x + 3) = 19? (5 points)
2 answers:
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Answer:
x = 2 cm
y = 2 cm
A(max) = 4 cm²
Step-by-step explanation: See Annex
The right isosceles triangle has two 45° angles and the right angle.
tan 45° = 1 = x / 4 - y or x = 4 - y y = 4 - x
A(r) = x* y
Area of the rectangle as a function of x
A(x) = x * ( 4 - x ) A(x) = 4*x - x²
Tacking derivatives on both sides of the equation:
A´(x) = 4 - 2*x A´(x) = 0 4 - 2*x = 0
2*x = 4
x = 2 cm
And y = 4 - 2 = 2 cm
The rectangle of maximum area result to be a square of side 2 cm
A(max) = 2*2 = 4 cm²
To find out if A(x) has a maximum in the point x = 2
We get the second derivative
A´´(x) = -2 A´´(x) < 0 then A(x) has a maximum at x = 2
