Halp me on my math plz

ABC bookstore sells one customer 12 used books and 4 new books for $120.

Ede4ka [16]

Answer:

One used book cost 5$ and a new book cost 15$

Step-by-step explanation:

$\left \{ {{12u + 4n = 120} \atop {14u + 2n = 100}} \right. \\$

lets multiply the second equation ×(-2)

× $\left \{ {{12u + 4n = 120} \atop {(-2)*(14u + 2n = 100)}} \right. \\\\\left \{ {{12u + 4n = 120} \atop {-28u - 4n = -200}} \right. \\\\\\\left \ {{-16u + 0n = -80} \\,\\\left \ {{16u = 80}\\,\left \ {{u = 5} \\\\$

if u = 5 then from equation 1

12*u + 4n = 120, 60 +4n = 120, 4n=120-60, n=60/4, n=15

7 0

4 years ago

Read 2 more answers

Please don't answer wrong.

Tamiku [17]

Answer:

<u />

<u>Equation of a circle</u>

$(x-a)^2+(y-b)^2=r^2$

where:

(a, b) is the center
r is the radius

Given equation: $x^2+y^2=6.25$

Comparing the given equation with the general equation of a circle, the given equation is a <u>circle</u> with:

center = (0, 0)
radius = $\sqrt{6.25}=2.5$

To draw the circle, place the point of a compass on the origin. Make the width of the compass 2.5 units, then draw a circle about the origin.

Given equation: $x+y=1.5$

Rearrange the given equation to make y the subject: $y=-x+1.5$

Find two points on the line:

$x=-2 \implies -(-2)+1.5=3.5\implies (-2,3.5)$

$x=2 \implies -(2)+1.5\implies-0.5\implies (2,-0.5)$

Plot the found points and draw a straight line through them.

The <u>points of intersection</u> of the circle and the straight line are the solutions to the equation.

To solve this algebraically, substitute $y=-x+1.5$ into the equation of the circle to create a quadratic:

$\implies x^2+(-x+1.5)^2=6.25$

$\implies x^2+x^2-3x+2.25=6.25$

$\implies 2x^2-3x-4=0$

Now use the quadratic formula to solve for x:

$x=\dfrac{-b \pm \sqrt{b^2-4ac} }{2a}\quad\textsf{when }\:ax^2+bx+c=0$

$\implies x=\dfrac{-(-3) \pm \sqrt{(-3)^2-4(2)(-4)}}{2(2)}$

$\implies x=\dfrac{3 \pm \sqrt{41}}{4}$

To find the coordinates of the points of intersection, substitute the found values of x into $y=-x+1.5$

$\implies y=-\left(\dfrac{3 + \sqrt{41}}{4}\right)+1.5=\dfrac{3-\sqrt{41}}{4}$

$\implies y=-\left(\dfrac{3 - \sqrt{41}}{4}\right)+1.5=\dfrac{3+\sqrt{41}}{4}$

Therefore, the two points of intersection are:

$\left(\dfrac{3 + \sqrt{41}}{4},\dfrac{3-\sqrt{41}}{4}\right) \textsf{ and }\left(\dfrac{3 - \sqrt{41}}{4},\dfrac{3+\sqrt{41}}{4}\right)$

Or as decimals to 2 d.p.:

(2.35, -0.85) and (-0.85, 2.35)

6 0

2 years ago

Does the choice of the base affect the area of the triangle

icang [17]

Yes the base of a triangle greatly affects the area of the triangle. Half of the base times the height of a triangle equals its area, so therefore the base greatly affects it.<span />

3 0

3 years ago

Read 2 more answers

Pablo's retirement party will cost $8 if he invites 4 guests. If there are 6 guests, how

mezya [45]

Answer:

$12

Step-by-step explanation:

Step 1:

$8 : 4 = x : 6

Step 2:

4x = 48

Answer:

x = 12

Hope This Helps :)

6 0

4 years ago

Identify the slope and y-intercept from the following equations.

Maksim231197 [3]

Answer:

y=3x - 1

M=3

B=1

y=1/2 X - 5

M=1/2x

B=5

8 0

4 years ago