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If (D(t)=120-kt) and (D(3)-D(9)=42), what is (k)?यदि (D(t)=120-kt) और (D(3)-D(9)=42), तो (k) क्या है?
Answer and explanationउत्तर और व्याख्या
Correct answer:सही उत्तर: 77
Given \(D(t)=120-kt\), we have \(D(3)=120-3k\) and \(D(9)=120-9k\). Hence, \(D(3)-D(9)=(120-3k)-(120-9k)=6k\). Since \(6k=42\), \(k=7\). If \(k=6\), the difference would be only \(36\), not 42. Exam tip: when subtracting function values, cancel the common constant terms first.दिया है कि \(D(t)=120-kt\)। अतः \(D(3)=120-3k\) और \(D(9)=120-9k\)। इसलिए \(D(3)-D(9)=(120-3k)-(120-9k)=6k\)। \(6k=42\) से \(k=7\) मिलता है। विकल्प 6 लेने पर अंतर केवल \(36\) होगा, 42 नहीं। परीक्षा टिप: दो फलनों के अंतर में समान स्थिर पद पहले काट दें।
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