Question

If 2a + 7 = 11 and ab = 2, find the value of 4a2 + 49b2.
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Answer 1

2a+7b=11

Squaring on both sides, we get:

$\sf (2a+7b)^2=11^2 \\\\\sf =4a^2+49b^2+28ab=121 \\\\\sf Putting~ the~ value~ of ~ \bf {ab=2} ~ \\\\\sf = 4a^2+49b^2+54=121 \\\\\sf =4a^2+49b^2= 121-54 \\\\\sf 4a^2+49b^2= 67$