The problem consists of two parts. (a) Solve the inequality $4 + \frac{3}{4}(x+2) \leq \frac{3}{8}x + 1$. (b) A rectangle $PQRS$ has dimensions $20$ cm by $(10 + x + 10)$ cm, i.e., $20$ cm by $(20+x)$ cm. A square of side $x$ cm is cut out. The area of the shaded portion is $484$ cm$^2$. Find the value of $x$.

AlgebraInequalitiesQuadratic EquationsArea CalculationFactorization
2025/4/19

1. Problem Description

The problem consists of two parts.
(a) Solve the inequality 4+34(x+2)38x+14 + \frac{3}{4}(x+2) \leq \frac{3}{8}x + 1.
(b) A rectangle PQRSPQRS has dimensions 2020 cm by (10+x+10)(10 + x + 10) cm, i.e., 2020 cm by (20+x)(20+x) cm. A square of side xx cm is cut out. The area of the shaded portion is 484484 cm2^2. Find the value of xx.

2. Solution Steps

(a) Solve the inequality:
4+34(x+2)38x+14 + \frac{3}{4}(x+2) \leq \frac{3}{8}x + 1
4+34x+6438x+14 + \frac{3}{4}x + \frac{6}{4} \leq \frac{3}{8}x + 1
4+34x+3238x+14 + \frac{3}{4}x + \frac{3}{2} \leq \frac{3}{8}x + 1
82+32+34x38x+1\frac{8}{2} + \frac{3}{2} + \frac{3}{4}x \leq \frac{3}{8}x + 1
112+34x38x+1\frac{11}{2} + \frac{3}{4}x \leq \frac{3}{8}x + 1
Multiply by 8 to clear the fractions:
8(112+34x)8(38x+1)8(\frac{11}{2} + \frac{3}{4}x) \leq 8(\frac{3}{8}x + 1)
44+6x3x+844 + 6x \leq 3x + 8
6x3x8446x - 3x \leq 8 - 44
3x363x \leq -36
x12x \leq -12
(b) The area of the rectangle PQRSPQRS is 20(20+x)=400+20x20(20+x) = 400 + 20x.
The area of the square cut out is x2x^2.
The area of the shaded portion is the area of the rectangle minus the area of the square:
400+20xx2=484400 + 20x - x^2 = 484
x2+20x+400484=0-x^2 + 20x + 400 - 484 = 0
x2+20x84=0-x^2 + 20x - 84 = 0
x220x+84=0x^2 - 20x + 84 = 0
We can solve this quadratic equation using the quadratic formula or by factoring. Let's try factoring:
(x6)(x14)=0(x - 6)(x - 14) = 0
x=6x = 6 or x=14x = 14
Since the width of the rectangle is 20+x20+x, and we have two segments of length 1010, we must have x<20x < 20. Both solutions are valid.

3. Final Answer

(a) x12x \leq -12
(b) x=6x = 6 or x=14x = 14

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