Geometry Matrices
1. **(A) Area of triangle using base and altitude:**
The area of a triangle is given by the formula:
$$\text{Area} = \frac{1}{2} \times \text{base} \times \text{altitude}$$
Given base $= 6$ and altitude, multiply by $\frac{1}{3}$:
$$\text{Area} = \frac{1}{2} \times 6 \times \frac{1}{3} = \frac{1}{2} \times 2 = 1$$
2. **(B) Area of rectangle (length × width):**
Area = length $\times$ width (no values given, formula only)
3. **(C) Formula for area of triangle with variables:**
$$\text{Area} = \frac{1}{2} \times x_0 \times 6 \times x = 3x x_0$$ (interpreted multiplication)
4. **(D) Multiplication for square:**
Side $\times$ side gives the area of a square.
5. **Types of triangles:**
- Scalene: مختلف الاطلاع (all sides different)
- Right Angled: قاعدہ الزاویہ (has a right angle)
- Equilateral: ساماں الاطلاع (all sides equal)
- Isosceles: تادلی الزاویہ (two sides equal)
6. **Adjoint of matrix**
Given matrix:
$$A=\begin{bmatrix}4 & -2 \\ -1 & 6\end{bmatrix}$$
Steps to find adjoint (transpose of cofactor matrix):
Cofactors:
$$C_{11} = 6, C_{12} = 1, C_{21} = 2, C_{22} = 4$$
Adjoint (transpose):
$$\text{adj}(A) = \begin{bmatrix}6 & 2 \\ 1 & 4\end{bmatrix}$$
7. **Calculate** $$(\frac{9}{16})^{-\frac{1}{2}}$$
Rewrite:
$$= \left(\frac{9}{16}\right)^{-\frac{1}{2}} = \left(\frac{9}{16}\right)^{\frac{-1}{2}} = \frac{1}{\left(\frac{9}{16}\right)^{\frac{1}{2}}}$$
Square root:
$$\sqrt{\frac{9}{16}} = \frac{3}{4}$$
Therefore:
$$\frac{1}{\frac{3}{4}} = \frac{4}{3}$$
8. **Correct answer for** $$(\frac{9}{16})^{-\frac{1}{2}}$$ is $\frac{4}{3}$.
9. **Logarithm of any number to itself as base:**
$$\log_a a = 1$$ (the logarithm of a number to its own base is always 1)
10. **Product of** $(\sqrt{x} + \sqrt{y})(\sqrt{x} - \sqrt{y})$:
Apply difference of squares:
$$=(\sqrt{x})^2 - (\sqrt{y})^2 = x - y$$
11. **Factors of** $a^4 - 4b^4$:
Rewrite:
$$a^4 - (2b^2)^2 = (a^2)^2 - (2b^2)^2$$
Apply difference of squares:
$$(a^2 - 2b^2)(a^2 + 2b^2)$$
12. **LCM of** $15x^2$, $45xy$, and $30xyz$:
Prime factors:
- $15x^2 = 3 \times 5 \times x^2$
- $45xy = 3^2 \times 5 \times x \times y$
- $30xyz = 2 \times 3 \times 5 \times x \times y \times z$
LCM takes highest powers:
- $3^2$, $5$, $2$, $x^2$, $y$, $z$
So:
$$LCM = 2 \times 3^2 \times 5 \times x^2 \times y \times z = 90 x^2 y z$$
13. **Solution of inequality** $-2 < x < \frac{3}{2}$:
$x=\frac{3}{2}$ (three halves) satisfies this as it is the upper bound.
14. **Ordered pair satisfying** $y = 2x$:
Check options:
- (2,1): $1 \stackrel{?}{=} 2 \times 2 = 4$ no
- (1,2): $2 = 2 \times 1 = 2$ yes
- (0,1): $1 = 2 \times 0 = 0$ no
- (2,2): $2 = 2 \times 2 = 4$ no
Answer: (1,2)
15. **Distance between** $(0,0)$ and $(1,1)$:
Use distance formula:
$$\sqrt{(1-0)^2 + (1-0)^2} = \sqrt{1 + 1} = \sqrt{2}$$
16. **Each angle of an equilateral triangle:**
$$60^\circ$$
17. **Diagonals of a parallelogram:**
Diagonals ______ each other.
Answer: bisect
18. **Bisectors of angles of a triangle are:**
Answer: concurrent
19. **Comparison of two alike quantities is called:**
Answer: proportion
20. **For matrix options given:**
Original matrix:
$$\begin{bmatrix}4 & -2 \\ -1 & 6\end{bmatrix}$$
Adjoint:
$$\begin{bmatrix}6 & 2 \\ 1 & 4\end{bmatrix}$$
21. **Summary answers:**
- $(\frac{9}{16})^{-\frac{1}{2}} = \frac{4}{3}$
- Logarithm base itself = 1
- $(\sqrt{x} + \sqrt{y})(\sqrt{x} - \sqrt{y}) = x - y$
- Factors of $a^4 - 4b^4$ are $(a^2 - 2b^2)(a^2 + 2b^2)$
- LCM is $90 x^2 y z$
- Solution of $-2 < x < \frac{3}{2}$ is $\frac{3}{2}$
- Point satisfies $y=2x$ is $(1,2)$
- Distance (0,0) and (1,1) is $\sqrt{2}$
- Equilateral triangle angles: $60^\circ$
- Diagonals of parallelogram bisect each other
- Angle bisectors of triangle are concurrent
- Comparison of quantities is proportion
Final matrix adjoint:
$$\text{adj} \begin{bmatrix}4 & -2 \\ -1 & 6\end{bmatrix} = \begin{bmatrix}6 & 2 \\ 1 & 4\end{bmatrix}$$