Question

7. If a + 2b =5, and ab = 2, find a² + 4a²
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Answer 1

Answer:

➡Given here.

↪a+2b = 5...........(1).

↪ab= 2..................(2).

➡Find here .

↪a²+4b²= ?.

➡Now,we know

♠(x+y)²= x²+2xy+y².

➡So,

▶(a+2b)²= a²+4ab +4b².

[ keep value by (2). and (1).]

♠(5)²=a²+4b²+4×2.

=> a²+4b²= 25-8.

=>a²+4b²= 17.