Concept-wise Practice

cross multiplication MCQ Questions for Class 12

cross multiplication se related questions ko ek jagah revise karein. Har question me bilingual content, answer feedback aur explanation available hai.

Practice Questions

2 questions tagged with cross multiplication.

यदि \(f:\mathbb{R}\to\mathbb{R}\), (f(x)=\frac{3x-2}{x+5}) और \(x\ne-5\) है, तो (f) के एकैकीपन के बारे में सही कथन क्या है?

If \(f:\mathbb{R}\to\mathbb{R}\), (f(x)=\frac{3x-2}{x+5}) and \(x\ne-5\), what is correct about the one-one nature of (f)?

Explanation opens after your attempt
Correct Answer

A. यह एकैकी हैIt is one-one

Step 1

Concept

Assume (f(a)=f(b)).

Step 2

Why this answer is correct

From \(\frac{3a-2}{a+5}=\frac{3b-2}{b+5}\), cross-multiplication gives (17a=17b), hence (a=b).

Step 3

Exam Tip

Cross-multiplication is very useful for fractional linear functions. चरण 1: मान लें (f(a)=f(b))। चरण 2: \(\frac{3a-2}{a+5}=\frac{3b-2}{b+5}\) से क्रॉस गुणा करने पर (17a=17b), अतः (a=b)। चरण 3: भिन्नात्मक रैखिक फलनों में क्रॉस गुणा बहुत उपयोगी होता है।

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फलन \(f:\mathbb{R}\setminus{1}\to\mathbb{R}\setminus{1}\), (f(x)=\frac{x+1}{x-1}) के बारे में सही कथन क्या है?

What is correct about \(f:\mathbb{R}\setminus{1}\to\mathbb{R}\setminus{1}\), (f(x)=\frac{x+1}{x-1})?

Explanation opens after your attempt
Correct Answer

A. यह एकैकी हैIt is one-one

Step 1

Concept

Assume (f(a)=f(b)).

Step 2

Why this answer is correct

\(\frac{a+1}{a-1}=\frac{b+1}{b-1}\) gives ((a+1)(b-1)=(b+1)(a-1)), leading to (a=b).

Step 3

Exam Tip

For fractional linear functions, cross-multiplication is a good way to test one-one nature. चरण 1: (f(a)=f(b)) मानें। चरण 2: \(\frac{a+1}{a-1}=\frac{b+1}{b-1}\) से ((a+1)(b-1)=(b+1)(a-1)), जिससे (a=b) मिलता है। चरण 3: भिन्नात्मक रैखिक फलनों में क्रॉस गुणा करके एकैकीपन जांचें।

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