Math Problem Statement

a^2+b^2+c^2=25, x^2+y^2+z^2=36, ax+by+cz=30, (a+b+x)/(x+y+z)=m. Find m

Solution

We are given the following system of equations:

a2+b2+c2=25a^2 + b^2 + c^2 = 25 x2+y2+z2=36x^2 + y^2 + z^2 = 36 ax+by+cz=30ax + by + cz = 30 a+b+xx+y+z=m\frac{a + b + x}{x + y + z} = m

Step 1: Let’s simplify the expression for mm

We need to find mm, where m=a+b+xx+y+zm = \frac{a + b + x}{x + y + z}.

From the second equation, we know that x2+y2+z2=36x^2 + y^2 + z^2 = 36. This implies that: x+y+z=36=6x + y + z = \sqrt{36} = 6

Now the expression for mm becomes: m=a+b+x6m = \frac{a + b + x}{6}

Step 2: Solve for a+b+xa + b + x

We need to calculate a+b+xa + b + x to find mm. Using the information from the first three equations, we aim to find values or relationships between aa, bb, cc, xx, yy, and zz.

Step 3: Geometrical Interpretation and Application of the Cauchy-Schwarz Inequality

The equations resemble the form of vectors, and applying the Cauchy-Schwarz inequality will help us determine the maximum or minimum values.

For the vectors v=(a,b,c)\mathbf{v} = (a, b, c) and u=(x,y,z)\mathbf{u} = (x, y, z), the Cauchy-Schwarz inequality states: (ax+by+cz)2(a2+b2+c2)(x2+y2+z2)(ax + by + cz)^2 \leq (a^2 + b^2 + c^2)(x^2 + y^2 + z^2)

Substitute the known values: 30225×3630^2 \leq 25 \times 36 900900900 \leq 900 This shows that equality holds, meaning that the vectors v\mathbf{v} and u\mathbf{u} are collinear. Therefore, we can express one vector as a scalar multiple of the other: (a,b,c)=k(x,y,z)(a, b, c) = k(x, y, z) for some constant kk.

Step 4: Determine kk

Using ax+by+cz=30ax + by + cz = 30, we substitute a=kxa = kx, b=kyb = ky, and c=kzc = kz: kx2+ky2+kz2=30kx^2 + ky^2 + kz^2 = 30 k(x2+y2+z2)=30k(x^2 + y^2 + z^2) = 30 k×36=30k=3036=56k \times 36 = 30 \quad \Rightarrow \quad k = \frac{30}{36} = \frac{5}{6}

Step 5: Solve for aa, bb, and cc

Now, using a=56xa = \frac{5}{6}x, b=56yb = \frac{5}{6}y, and c=56zc = \frac{5}{6}z, substitute into the equation a2+b2+c2=25a^2 + b^2 + c^2 = 25: (56x)2+(56y)2+(56z)2=25\left( \frac{5}{6}x \right)^2 + \left( \frac{5}{6}y \right)^2 + \left( \frac{5}{6}z \right)^2 = 25 2536(x2+y2+z2)=25\frac{25}{36}(x^2 + y^2 + z^2) = 25 2536×36=25\frac{25}{36} \times 36 = 25 This confirms the values of aa, bb, and cc.

Step 6: Find mm

We can now calculate a+b+xa + b + x: a+b+x=56x+56y+x=116x+56ya + b + x = \frac{5}{6}x + \frac{5}{6}y + x = \frac{11}{6}x + \frac{5}{6}y Thus, using all terms computed

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Algebra
Geometry
Inequalities
Vectors

Formulas

a^2 + b^2 + c^2 = 25
x^2 + y^2 + z^2 = 36
Cauchy-Schwarz Inequality: (ax + by + cz)^2 ≤ (a^2 + b^2 + c^2)(x^2 + y^2 + z^2)

Theorems

Cauchy-Schwarz Inequality

Suitable Grade Level

Grades 10-12