Concept-wise Practice

careful-calculation MCQ Questions for Class 10

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Practice Questions

2 questions tagged with careful-calculation.

समीकरणों (4x+3y=34) और (2x-y=4) के लिए (x) का मान क्या है?

For (4x+3y=34) and (2x-y=4), what is the value of (x)?

Explanation opens after your attempt
Correct Answer

C. (x=5)

Step 1

Concept

From the second equation use (y=2x-4). Correct substitution gives (4x+6x-12=34), so \(x=\frac{23}{5}\).

Step 2

Why this answer is correct

The correct answer is C. (x=5). From the second equation use (y=2x-4). Correct substitution gives (4x+6x-12=34), so \(x=\frac{23}{5}\).

Step 3

Exam Tip

दूसरे समीकरण से (y=2x-4) रखें। पहले में रखने पर (10x-12=34) नहीं, सही गणना (4x+6x-12=34) से \(x=\frac{23}{5}\) आती है।

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यदि \(x=2+\sqrt{7}\), तो \(x+\frac{1}{x}\) का मान क्या है?

If \(x=2+\sqrt{7}\), what is the value of \(x+\frac{1}{x}\)?

Explanation opens after your attempt
Correct Answer

A. \(2\sqrt{7}\)

Step 1

Concept

\(\frac{1}{2+\sqrt{7}}\) equals \(\frac{2-\sqrt{7}}{-3}=\frac{\sqrt{7}-2}{3}\). So \(x+\frac{1}{x}=2+\sqrt{7}+\frac{\sqrt{7}-2}{3}=\frac{4+4\sqrt{7}}{3}\).

Step 2

Why this answer is correct

The correct answer is A. \(2\sqrt{7}\). \(\frac{1}{2+\sqrt{7}}\) equals \(\frac{2-\sqrt{7}}{-3}=\frac{\sqrt{7}-2}{3}\). So \(x+\frac{1}{x}=2+\sqrt{7}+\frac{\sqrt{7}-2}{3}=\frac{4+4\sqrt{7}}{3}\).

Step 3

Exam Tip

\(\frac{1}{2+\sqrt{7}}=\frac{\sqrt{7}-2}{3}\) नहीं बल्कि हर (4-7=-3) से मान \(\frac{2-\sqrt{7}}{3}\) है इसलिए सीधा विकल्प नहीं बनेगा। सही सरलीकरण जांचे बिना उत्तर न चुनें।

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